I checked the same on Windows 10,Lightroom 5.7.1 and it is working fine.
Have you checked the keyboard itself?
If that does not help reinstall Lightroom and let us know if that helps.
Thanks for suggestion, Akash. I downloaded LR 5.7.1 installed (from Adobe - Lightroom : For Windows : Adobe Photoshop Lightroom 5.7.1 ), ran the installer using "Repair" option, problem not fixed. Keyboard +/- keys work fine on other programs (MS Word, email, Powerpoint, Excel, Notepad, etc.).
Any further suggestions appreciated, thank you!
Try resetting the preferences.
With Lightroom closed, use Windows Explorer and navigate to
C:\Users\[Your user name]\AppData\Roaming\Adobe\Lightroom\Preferences
Delete the file Lightroom 5 Preferences.agprefs.
Launch Lightroom, which will now rebuild the preferences.
Note that you will lose any customized settings in the preferences, but LR preferences are not very extensive, and should be easy to recreate. You can go into preferences (Ctrl+,) before you delete them and make a note of your settings if you like.
Thanks, Per, appreciate the suggestion, but sorry to report it didn't fix the problem.
Any other suggestions appreciated, thank you!
Hi I have the same issue, any luck with fixing this. I found that if you hold ctrl and then use the mouse wheel that works but as you not with the + and - keys.