Hello and sorry, unfortunately in trying to work I did try and reinstall the blender to eliminate the error, which is now gone; (. I tried to replicate the error but I can't.
However, I noticed that, to delete error it was not necessary to reinstall blender, but only to delete the folder "C: \Users\%USName%\AppData\Roaming\Blender Foundation\Blender\2.90\*". Blender auto-regen it and the error disappear.