I had a 13 character alpha-numerical password. I no longer have the issue as I have upgraded my router.

@Kevin_Z Router does not support TP-Link ID login. Login to router wirelessly locally. iPhone iOS 14.4.2 Tether Version: 3.4.28 (build 34) Error message is just a box saying "Incorrect Password"...

Since the latest update of the app it reports an incorrect password error. I have not changed the password or any router settings and can login ok via web browser. Have tried changing password but...