Who I have the same questioned this topic

I installed the latest version of message+ on my Galaxy Tab A with Android 7.1, but Message+ almost always starts in split screen mode (conversations on left and recent contacts on right).  When I open Message+ I can see that it tries to open in landscape and then quickly switches to portrait, but the interface stays in split screen.

Is there a way to disable this function in Message+?  I tried reinstalling the app and turning off "auto-rotate" on my device, nothing worked.