Prisma doesn't let me use old photos

A

AC Question

My Galaxy S Note III with Android 5.0 won't let me pimp my old images with Prisma.

When I click the image icon below right, it opens my photo albums, but when I click on a pic to use Prisma on it, it won't open, but instead I'm just taken to picture-taking mode in Prisma.

I have given all the rights to the app as I downloaded it.

Can anyone help, please!