That is the limit of sessions per named user/license: Assign ArcGIS Pro licenses in ArcGIS Online—ArcGIS Pro | Documentation
You can end a member’s active ArcGIS Pro session. This may be useful when a member is signed in to ArcGIS Pro on three computers at the same time (the maximum allowed) and needs to sign in on another computer. If the member is unable to sign out on one of the computers—for example, because the member is not physically present—you can end a session. This enables the member to sign in on another computer.
Ok thanks. Is there any way to override this and have more active sessions? I need more sessions of Pro to help with a very large processing task and have Pro open on 3 separate VMs.