suddenly the green blue button in imovie not working. any solutions

Hi, karthikeyan261,

There have been several reports of glitches after updating to iMovie 10.1.15 or 10.1.15. If that's your situation it may be that Apple will need to do the fix. However, there are other reasons that can cause iMovie features to malfunction.

First, what steps are you taking to activate the green screen feature and what happens when you do?

Meanwhile, try deleting preferences and see if that helps. To do that, open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects.

Restarting your computer might also help.

-- Rich

I think that the green screen issue is something that Apple will need to fix, as it may be related to the recent updates. If you have tried all of the diagnostic procedures in the link I posted, without success, then I am out of suggestions at this point.

If you have a Time Machine backup you could restore your previous iMovie version.

-- Rich

Also, take a look at this thread link and see if any of the diagnostic procedures that I listed there help you:

https://discussions.apple.com/thread/251872162

-- Rich