The develop module just suddenly stopped working. I use lightroom almost daily. I imported a new group of photos in Library and went to Develop as usual. I see the photo on the screen, as usual, but ant changes I make, like exposure, do not change the photo. I try to crop the photo and it vanishes, replaced by solid gray. I'm editing raw photos from a Nikon D600. Using Windows 10. Again, I use it regularly. Have not made any system changes. Develop just suddenly stopped doing anything.
This could be caused by a defective monitor profile, delivered by a Windows update, or installed when upgrading to Windows 10.
You can (temporarily) set the monitor profile to sRGB, if this fixes the issue, it's a confirmation that the profile is bad.
You should then ideally calibrate your monitor with a hardware calibrator, which will create a new, accurate profile .
To set the monitor profile to sRGB:
Press the Windows key+R, enter colorcpl, and hit Enter.
Add the sRGB profile, then set it as Default profile. See screenshot (from Windows 7) below.