étalonnage version 5

"as soon as I make a modification, they go back to gray."

Many have reported similar symptoms:

https://community.adobe.com/t5/lightroom-classic-discussions/p-gray-negative-image-display-in-the-develop-module/m-p/13006731

If your gray images in Develop look like those posted in that thread, then try the solution that worked for them: First,  set the option Preferences > Performance > Use Graphics Processor to Off. Then update your graphics driver by going directly to the manufacturer's web site, as described here:

https://helpx.adobe.com/lightroom-classic/kb/troubleshoot-gpu.html#solution-4 

Let us know whether this helps. If it doesn't, please provide System Information requested by GoldingD.

Also, see:

https://community.adobe.com/t5/lightroom-classic-discussions/p-gray-negative-image-display-in-the-develop-module/td-p/13006731

Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.

Can you provide more information? Do you have any pending updates? When did this begin? Have you completeley power cycled your computer? Where are your original image files located?