This happened to me not only 2 days ago. I fixed mine now and I'm glad someone has the same problem and I can help them. I tried everything and the only thing that would resolve my problem was to reset my phone to factory settings.
I used an app tool to backup my apps into sd card. Unfortunately, internal memory couldn't be backed.
I had to backup everything on my SD card before I did anything so my pics, music, the apps I had backed so they didn't wipe out after the reset.
I then went into settings-privacy and factory data reset. But I was warned it will erase phone data including my Google account which would also delete my apps that that account was connected to in the play store. I went into Gmail which was an app already installed on my phone, and i made a new account which I'd hoped would be the one to be deleted instead of my alternative Google account/email.
Then I hoped for the best and clicked the reset to factory settings. Check the sd card as well, I didn't worry cuz i had already backed everything off my SD onto my hard drive.
My phone had wiped off everything, my pics, music on sd including my apps, but uckily I had backed those up earlier.
When you first turn on your phone, there will be a Google account thing saying Whether to login to an account you already have or signing up to a New one. Of course I clicked on that and logged into my normal account. Luckily the account hadn't deleted and i still have it. Hooray for me. I think this was because I created another Google account earlier in hope that it would delete that one. Haha
i started afresh, putting my stuff that I had backed earlier back onto my sd card. And the gallery IMG doesn't show the red lock, my pics are finally showing , and my music is finally playing.
hope this helps for anyone else out there.
Keep in mind, my contacts were not removed, they're still there, so are my things like Google account, and pics apps, music cuz I backed those up.
Just remember to back things up before reset and you'll be fine