Can't connect to dongle after network change - password required

I had problems with my old router, and after an internet outage the dongle and several other devices would not connect to my network no matter what.
I've got a new router, and am trying to connect my phone to the dongle, but it's now asking me for a password, which it wasn't asking me for before.
I've tried the serial number as the password and couldn't connect.
Any idea how I can fix this?

I've managed to connect to the dongle now, but when the app tries to connect to our home network it can't identify it.
Any thoughts on what I can do to fix it?

Theres a few suggestions on this thread

https://community.givenergy.cloud/d/2302-new-wifi-no-dongle-connection

Plus a few other topics on the same issue can be found in the search facility.