Welcome to Flyertalk and welcome to the BA Forum.
It's not that unusual, and it may simply work in a few hours from now.
There is this thread which may help, but the one thing that is always worth checking is whether there is a ticket number on the BA App, when you go to the details panel, and it's a number usually beginning 125,
https://www.flyertalk.com/forum/brit...ficulties.html