Join Request problem

Yes.

A DevAddr as generated by TTN should start with 26 or 27 (hexadecimal). (As an aside: these are not a secret; anyone can pick them up from the radio transmission.)

Then you’re erroneously using a DevAddr that starts with 00, 01, 02 or 03, or you entered it in the wrong order. You should use the DevAddr as issued by TTN, and choose the right option: Hex, lsb or msb? (Check the 2 working nodes).