Have you tried to use the masking in a new catalog?
If the issue still persist in a new catalog then you can try to reset Lightroom preference by holding the shift + option (Mac) or shift+alt (Windows) while launching Lightroom.
Let us know if it helps.
Thanks for your help and interest with my masking issue. Unfortunately resetting prefs didn't fix the issue. I found my old Lightroom 4 and it was working correctly however since it cannot open current catalogs its but much help.
If you have any other suggestions That might help please let me know, this is one if those pull your hair out problems in have to resort to masking in PS then reimporting to LR. Btw I am on Mac running Yosemite OS X 10.5.5
Thanks again -dC
Sent from my iPhone
Could you please share the develop panel settings that you have applied on your mask with us.
Just following up on my my case.
After upgrading to LR 6.3 the making issues mysteriously disappeared. When I first upgraded problem was still present, however after using LR 6.3 for a short time masking issues were gone. This is weird but a good thing, so after 3-4 days of using it the issues have not returned and somehow the problem solved itself. Thank you for your help on these issues. all the best. Happy holidays. -dC
You too have a Happy Holidays