Amazon Apps

Ever since Marshmallow, my Amazon apps (Kindle, Music, Video) won't update. The update downloads but does not install. Then a day or two later, I am reminded by the phone of the updates. Music and Kindle are installed from Play. Video is installed from Amazon. I tried restoring Music to factory settings. Updates still won't install. I tried uninstalling Video. I cannot reinstall. I am on Verizon. Any thoughts?

Edit: Play is giving a 505 error. Tried forced stop/cleared cache.