I note only us three have flagged this. I wonder if you have found a solution?
The app has ALWAYS previously been able to change orientation.
I think it's since the last update, I have a new iPhone XR which will not change to landscape and I still have my old iPhone 6SPlus which is the same.
But this is not a new install, it was restored from the old phone.
I will contact support to find out wether this is a new limitation or a glich that can be fixed.
Very often a fresh install fixes things and you have to restore your user presets from your backup. Steve