When connecting to VitalPBX, the “Multi-tenant“ option in the Ringotel connection settings should be disabled to ensure that calls are routed correctly.
When the "Multi-tenant" option is enabled, Ringotel sends REGISTER message with a local domain name in the Contact header. In compliance with RFC3261 Ringotel expects to receive INVITE URI with the corresponding domain name to route calls to the corresponding organization and user. Otherwise, it could lead to incoming calls being rejected.
From what we see, VitalPBX does not specify a domain name in the Contact header. Thus calls could not be routed correctly.