Usually that means the radio has failed and needs to be RMAd.
When you upgraded, did you do a factory reset, update then factory reset once more? I might try this process once more if you didn't.
I might try to change the mode from Mixed ALL to single mode G, use open security to test. If you still can't seem to get connected to the radio and the "Init Failed" message still appears, RMA it. Not sure how much longer these routers will be supported as they have now hit EOL.
Since the LAN and router portion of the router is still working and if you can't get an RMA on it, I would recommend keeping the router, turn OFF the radio and get a DAP-1360, 1522, 1525 or 1533 and connect it to the 655 and this will be your new wireless radio.
Let us know how it goes.