I have the same issue.
We have VSX R80.20 which has a number of VS's and VSW's. The NMS we are using is SolarWinds. I don't currently have VS mode on from an SNMP view. as I want to firstly understand what has to be done not only on a VSX side but also on the SolarWinds side.
At the moment we can poll the appliance (VS0) using SNMPv3 without issue, but when I last tried VS mode on this stopped polling.
My objective is to monitoring the health of the appliance and also monitor VS's ie monitor the interfaces, connection table, bandwidth.
There is a SK from 2016 which implies SolarWinds does not work with Checkpoint VSX, not sure if this really is still relevant, if not then it should be updated.
Are there any actually whitepapers that go through setting monitoring with different NMS?