Hi Uwe, I have good news for you… I’m so happy!
2 hours (!!!) spent with the Regedit, looking for “skp” … and many many others things under that 3 letters. I should have started with “.skp” or “sketchup” … that I did after.
I deleted about 80 entries … 2 of them were refused (even trying to change the rights… no way)
Then I rebooted,
and I reinstalled the last Sketchup 2021, in admin mode.
Everything came back !!!
I’m so happy, it will save me lot of time.
So again, thanks for your support and all your knowledge (maybe intuition !).