If you have already updated to Marshmallow, then chances are that you are often spotting a thing or two out of place, or just not proper as it should be. Example in case being Google+ app, which might not be showing proper icons or thumbnails to you of person the way it used to.
Another example could be Facebook messenger unable to show Chat heads, whose fix we covered in our Marshmallow issues post here. All you need to let messenger show the chat heads in overlay style was enable the ‘draw over other apps’ feature in Apps settings.
The issue with Google+ apps, and many other apps is about permissions — or their mismanagement — only.
If you are experiencing the issue with any app on Android 6.0 Marshmallow, then we suggest you check what permissions it got, and what are not enabled for this even when it should obviously have them.
How to Fix
So, in our Google+ example, go to Settings > Apps > look for Google+ app and tap on it > Permissions, and now provide it the required permission.
If you can’t figure out what required permission is, then simply enable all, and then try the app again. Then, you could disable the permissions you won’t want to have access to for the given app. For thumbnails, enable the Storage permission btw.
Other apps in which you could be facing similar issues over permissions could be: Falcon Pro, Hangouts and Facebook messenger. Also the camera app, which couldn’t be showing previews as it should when camera is opened.
The fix is, you have to check permissions enabled for the app, and if see a permission or two disabled, then enable them so that apps could work as it should.