Firestick can’t connect to new wifi and have no remote

The Firestick and phone have to be on the same network in order for the app to work. Once you reset or changed your WIFI it severed the connection. Most TVS now have the HDMI -CEC connection which allows your firestick remote to control your tv but it most cases it works the other way around where your tv remote is able to control some functions on the fire stick. Try that maybe it will work for you if not then unfortunately it looks like you would have to get a new firestick remote and pair it with your firestick.