Ever since the last two updates, I can no longer install any addon manually like I used to. I would be able to update the Youtube Center addon from Github by downloading the .xpi file then opening it from a File Explorer. However, all I get is a blank screen, no message asking if I want to install or confirming that it was installed. I read somewhere that binary files for some addons could be installed, but I am unable to find any for Youtube Center on the developer's page. I have ALWAYS been able to use the .xpi file from Github on FF Android with Zero problems until FF 43 for Android. The version you have listed on your AMO is extremely outdated and is no longer compatible with FF for Android and destroys functionality of the site. Also some addons listed on the AMO won't even install though they say they are for FF Android. I even tried using FF Android Beta and could not get Youtube Center to install. I am yet again disappointed with Mozilla's Android version of FF which has always been a disgrace IMHO.