When setting the Telescope focal length on the Mount Tab, you must click on the Save Telescope Info button for it to be applied. Verify it is correct with expected FOV in the alignment tab. It should update the telescope info in the INDI driver at the same time, so save the INDI driver configuration for next time.
Simulators aren't particularly useful for testing the polar align assistant either because by default they don't have much, if any, error.
Do, take the time to get your real mount, camera and guide camera connected and working and try it with real stars. 90% of the time, failed solves have to do with missing indexes, incorrect telescope and camera information, wrong scope/camera combo selected, underexposed frames or bad focus. There are also different solver profile defaults, try them all to see which works best for your equipment.
Sometimes it helps to uncheck Use Scale in the options. This will be slower, but more reliable if your telescope info is inaccurate. Once it tells you what the focal length truly is, you can save the updated telescope info and re-enable Use Scale.

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