Fortunately this is an easy fix.
EACH DEVICE requires a separate SIP account from Anveo. (ask me how I know)
On your Anveo dashboard, add subaccounts for each device, then get the SIP account info for that subaccount after verifying 911, etc as required to setup the account.
So you will have a UNIQUE SIP account number and password for EACH SP slot on each device.
As comparison, Google Voice allows up to 6 devices to share the same credentials. Anveo is one per account/subaccount.
You may have to add additional subaccounts subscription, depending on what you have. I think they are $1-.50 per month, per account when purchased in groups of 5, 10, 25, etc
FYI. Anveo supports call routing and PBX like features. Having one account per SP, per device allows calls to be controlled and routed to individual SP/devices.
I don't have my Anveo account in front of me at the moment, but if you need more details directions, just ask