File upload control not working in Facebook In-App Browser

Question

I have a mobile html Facebook app which has a control to upload files (a simple input file). I can upload fine when I open the app in a browser like this apps.facebook.com/m

Answer 1

I've faced the same problem, however it wasn't the multiple or accept attributes but whether the user has given then underlying app (Facebook, Messenger, IG,...) permission to access photos. Any idea how you can construct a fallback for that scenario?