An admin group can grant product access to multiple products. This error message is presented when trying to add a user to a group e.g. administrators and is blocked due to licensing limits on 1 or more products (in most cases I have seen, it is related to Statuspage).

The console returns an error such as:
resourceOwner=statuspage, resourceType=site, resourceId=[REDACTED_ID]}, availableLicencesWithinSoftLimit=-20, availableLicencesWithinHardLimit=-20, requiredSeats=1

We should be able to present this (Statuspage) product that has reached its limit, to the user rather than let them figure out which product is blocking the group addition.