For anyone else getting this error, I noticed there's hardly any info on it. I just solved mine.
First, uninstall the app and reinstall.
Open remote play app
Open settings menu on ps4
On ps4 go to Remote Play Connection Settings - Add Device - will show a number.
On app click 3 dots menu on top right corner, register manually, enter number from ps4.
This solved mine instantly, hope it helps.
