No, the credentials are generic not account specific.
You don't need to set the vlan id, that is a modem function.
I assume you have tried a different Ethernet cable between modem and router in case that is the problem.
Try 8.8.8.8 and 8.8.4.4 for DNS servers.
Does the Huawei modem work with the hub in FTTP mode?
OK so removing the VLAN ID has given me a valid connection! I left the DNS servers as "auto" but it also works if I specify my preferred server (9.9.9.9).
Sharing my settings here for other Unifi users: