Maybe the Seestar is set up to use 5GHz and your phone only have 2GHz for the WiFi?
Connecting using your PC with a cable only give you access to the files.
I have less issues with connection now than for 3ish firmware updates ago.
If i have trouble i usually always put the phone in flight mode and turn off WiFi. Start the app after i'm sure that it has been completely closed and not running. Either forced or by restarting the phone. Start the Seestar and turn on WiFi when it says its ready to connect. Then i go back to the app and it works. Then i can tuen off flight mode etc.
But if the real problem is that your seestar has another password for the BT then i'm not sure how you can reset this from the app. Not sure why you would change this as its required for you to press the BT button to link it to a phone so its not a security issue leaving it to the default.