C4000 modem with solid amber LED and internet in walled garden

I'm an ex-Century Link customer migrated to Quantum Fiber. I had to hard reset my C4000 modem, and it went to solid amber LED and walled garden.

I'm not able to get to connect.centurylink.com since my account is with Quantum Fiber now. I was not expecting not to be able to reset my connection but here we are.

I contacted Quantum Fiber customer service, and the only thing they can do apparently is sending a technician in 5 days to replace the modem...

Is there anyone who would have an idea on how to solve this set-up issue?