Solved. I will apply the solution here if anyone is interested.
During the conversion enter --console for the console to appear when you run the exe file. (pyinstaller --console filename.py)
When you run the exe and face an error like me, the error will appear on the console screen.
For me it was the missing icon files of the new windows that I forgot to add in the final file that contains exe and all the additional files (photos, databases etc).
That's it, it worked!