You are right, I didn’t think of making the changes in the profile. Here is my configuration.
Sketchup Pro 2020
OS Mojave 10.14.6
iMac Pro / Intel Xeon W 3,2 Ghz / 32 Go DDR4 2666 Mhz / Radeon Pro Vega 56 8 Go
I tried again and this time it works!? It seems to me to be random such as the icon preview with the QuickLook generator issue.