Soundstation IP5000 SIP Configuration

I have a Soundstation IP5000 that I am trying to configure for SIP.

Phone details:

Phone ModelSoundStation IP 5000

Part Number3111-30900-001

Rev:HMAC Address00:04:F2:FA:C8:9C

IP Address10.10.0.155

UC Software Version4.0.13.1445

BootROM Software Version5.0.13.0801

When I check the log I see:

Registration failed User: 881095, Error Code:480 Temporarily not available
Registration failed User: 881095, Error Code:400 Bad Request

I am connecting to a Avaya CS1000, there is no password setup on the phone switch. BTW, 881095 is the extension number.

Any help you could provide would be appreciated.