To quote the manual: The usable range for plate solve function is based on Field of View (FoV - combination of focal length of scope and sensor size) which has to be within 0.2 deg to 33 deg.
https://www.yuque.com/zwopkb/asiair/plate-solve
Because your FOV is only 0.31° x 0.18° then it may not plate solve successfully.
If you were to add in a f/6.3 focal reducer then your FOV would be 0.5° x 0.28° which should plate solve.
A f/7.0 focal reducer would give you a FOV of 0.45° x 0.25° which should plate solve.
So I recommend you use a focal reducer of at least f/7.0.
Tool used to calculate FOV: https://astronomy.tools/calculators/field_of_view/
