@Solla-topee Hi Solla, This issue appears to have resolved itself over night, perhaps an IP lease renewal issue? Here are the settings you asked after.

Dear Forum, I have an Archer C5400 and v1 RE450. The C5400 is working fine, but where the RE450 will connect to the router it cannot establish a connection to the internet. Any device connected to...

Nuts.... Should have read the earlier posts....

@MuruSK. This is an awful limitation, seeing devices from visitors who've only ever connected to the router once. I plan to export the router setting to a file, factory reset and the reload saved...