As stated when you ordered our services, including a checkbox to tick near the OS selection, your other IPv6 addresses will be provided in a timely fashion - maximum 48 hours (full week - this is treated as a Level 1 request).
This is due to a SolusVM 2.0 known bug, where the configurable option of adding IP addresses communicates still via API v1 (the platform connects via API v2) and it's only available for IPv4 addresses available on a pool, not for IPv6 as our offer allows (in CentralVPS and ExtraVPS). As such, this is added manually by our services.