Same problem. Unfortunately the W10M app is not very good.
Sure, they have updated a few times, but the original bugs still exist. I have gone back to the WP8 app.
Notifications work better, but still can't post from the app....
The W10M train is just about to reach it's final destination. After that I will retire my 1520 and get a feature phone.
Android and iOS don't look like a good option for me... All good things must come to an end...