Nighthawk app says router not found for R6700

Hi, for some reason my nighthawk app can't see my router R6700 anymore. Router works fine. The app says:

Issues connecting with XXX. Go to settings wifi bla bla bla. But my phone is using the same wifi network as router. New system setup says router not found and I don't have QR code.

P.S. I rebooted router and issue gets solved. Topic is closed.