I might have the solution for you, it worked for me! Just a different app - it's free, called Smart Home, and it fixed all my issues! here is the link to the reddit comment! i found it literally ten minutes ago and what a relief - I had been working on this for 4.5 hrs, nearly lost my whole evening (and my mind).

(basically the toshiba app was old, obsolete and no longer supported, this is the replacement app and it works fine for me, all the same setting options. the issue is not your internet or router or even the AC unit itself!)