ASI533MC Pro — ASICAMUSB3.sys blocked by Windows 11 after recent update

77gbBkjx

Hi,
I have a ZWO ASI533MC Pro camera which suddenly stopped working on my Windows 11 laptop.
The camera worked previously on the same computer. Now, immediately after connecting it, Windows shows a warning that the driver is blocked / cannot be loaded.
The blocked driver file is:
ASICAMUSB3.sys
My setup:
ZWO ASI533MC Pro
Windows 11 laptop
camera connected directly by USB, no hub
camera powered with external 12V power supply, as usual
latest ZWO camera driver installed
ASIStudio installed/reinstalled
What I already tried:
disabled Memory Integrity / Core Isolation
disabled Microsoft Vulnerable Driver Blocklist
uninstalled and reinstalled ZWO drivers as Administrator
uninstalled ASIStudio
removed hidden ZWO/ASI devices from Device Manager
tried removing old driver packages with pnputil
checked Driver Store Explorer / RAPR — no obvious ZWO / asicamusb3 entry visible
uninstalled recent Windows update KB5087051
restarted many times
The issue still persists. As soon as the camera is connected, Windows blocks ASICAMUSB3.sys.
Recent Windows updates installed just before the issue appeared:
KB5087051
KB5089549
KB5092762
One of them cannot be uninstalled because Windows marks it as required.
Has anyone experienced the same issue with ASICAMUSB3.sys on Windows 11? Is there a known working ZWO driver version or workaround?
I would really appreciate any advice.

38CAzzP2

Did you get this resolved yet?? I have the exact same issue from what I can see.

Installing driver on a new mini PC. I have the older one still that has the ASICAMUSB3.sys driver file present on the system and it's been working fine.

Meanwhile on the new PC, the install completes but I get the "blocked by windows" pop-up as soon as the camera connects and the device remains yellow banged in device manager and unusable.

This seems like a BIG problem! If there's no version of the installer/driver that will work with the present version of Windows. My camera is difference than yours (ASI120MM). The driver package is the same though. By inference, it seems like ALL ASI cameras would run into this same issue with current Windows if there's no software that passes whatever gate Windows is applying here. Would love to be wrong about that of course 😉

R712O2eO

Same problem here i have a 2600 camera and now i dont know what to do.

38CAzzP2

That's 3 different cameras with the same problem. Now it's really starting to look like this will affect anyone trying to install the native driver for any ASI camera. The Windows "more info" for this when the driver load fails says that it's a problem with the signature on the driver. Only ZWO can fix this.

I think we're all stuck until ZWO takes action!

johnpd

Check the following:

Open "Settings" > "Privacy and security" > "App and browser control" > "Smart App Control".
Click on "Smart App Control settings".
See if "Smart App Control" has been turned "ON".
If it has, turn it "OFF"..

This is a new feature added to Windows 11 and in some cases has recently been enabled (one case is if you have a new computer). What it does is verify that programs, parts of a program, or drivers are not malicious. It does this by checking in their cloud intelligent security service as to whether the software is safe. If they have no info on the software, they check to see it has a valid Windows signature. If that cannot be determined, it blocks the software. Currently there is no way to tell Smart App Control to ignore that piece of software like most antivirus have as an option.

JohnD

R712O2eO

johnpd
I did that and remained the same, I have de disable almost every security fixture and nothing, almost 2300 worth of imagin gear to be stocked this way.

johnpd

Can you display what the exact message is so we can get an idea of which Windows check is causing this? There are a few other possibilities. Core isolation is one. Microsoft apparently enabled all this junk with the last update last week.

JohnD

38CAzzP2

This is the "for more info..." link that is in the dialog box that pops up. Maybe that's more useful than the actual dialog box itself??

https://support.microsoft.com/en-us/windows/the-windows-driver-policy-ecd2a78c-750c-415d-93f2-e37302ce0443

If this is to be believed then the problem is the signature on the driver and it seems like no amount of tweaking Windows settings will help.

johnpd

Whoa, this is becoming bigger than a breadbox. I checked my Event Viewer that is specified in that Microsoft link. What I found was a .DLL for my antivirus software that was being accessed was considered "not meeting the Windows signing level requirements". These messages started on the 19th which apparently is when these checks were unleashed. I think a lot of software may have an issue.

JohnD

paolo77

I'm having the same problem with an ASI 224 mc. I recorded footage until April 25, 2026, then after some Windows 11 updates, it blocked the drivers, even the latest ones downloaded from the download area. I've tried everything: registry keys, BIOS, and Windows security settings, but nothing works. I'm working with an older Windows 10 laptop that has a USB port that won't let me go above 42 fps. Better than nothing.

johnpd

Yep, all of a sudden MS is getting tough on unsigned or not properly signed drivers.

JohnD

EKa

Same issue here with an ASI678mc using windows 11. Camera still works fine in OS X.

raul-supernova

Posted a fix here https://bbs.zwoastro.com/d/26665-asi-driver-issue-with-windows-11/5

38CAzzP2

raul-supernova - thank you. I have it working now. Posted in that thread. For me, less work than was suggested there ended up being needed. I was able to get the camera driver working properly through use of just the bcdedit commands, no startup changes needed other than a reboot.

@ZWO - to get this working we are all making our copies of Windows less than secure. This is not good and really needs to be a short term workaround. Please fix the problem with the signature on your driver as soon as you can!

Stephen Heliczer

Nope, not fixed for me... I have spent hours on this.... None of the above solutions work. I have disabled secure boot in Bios, disabled driver signature enforcement, applied nointegitychecks on and testsigning on in adminn mode command prompt, added folder to Windows Defender. And having to faff about with BitLocker in the process and blocked sign ins... Driver still comes up with ERROR 39 after all this work. Hopefully ZWO can fix the camera drivers! I am currently without my 462mc, 174mm, 585mm, 585mc, 2600mcPro cameras on my brand new top-spec i9 5080 laptop. Three clear nights ahead, no cameras.... 🙁

LyZx7EM5

I got the same problem with all my zwo cameras, 2600, 183, 533 and 120. I tried to disable the boot security like it said only to have my computer stop working and telling me no boot media was found. Very frustrated that windows can just decide to update without asking me and then blocking drivers i have been using for years, and now having a 500$ computer the requires me to find some sort of BitLocker recovery keys to get working again.