Why is the develop preview dark and it looks normal and expected in library? There are no changes happening in settings - no presets being applied, just darker when i move over to develop. can anyone help?
Could you please confirm which version of Lightroom are you using?
Which operating system : windows or mac?
When Library and Develop don't display identically, it's always because of a broken monitor profile.
Calibrate your monitor with a hardware calibrator, which will create a new, sound profile.
As a temporary solution you can set the monitor profile to sRGB as explained here: