We're on LICMAN 2018 and had a similar problem, resulting in BUG-000116524 Currently borrowed ArcGIS Pro extensions will not allow other logon accounts to use the extensions when disconnected from the License Manager.
The workaround is to run:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\ESRI\ArcGISPro\Licensing\Extensions]
"3D Analyst Pro"=dword:00000001
"Data Reviewer Pro"=dword:00000001
"Defense Mapping"=dword:00000001
"Geostatistical Analyst Pro"=dword:00000001
"Network Analyst Pro"=dword:00000001
"Production Mapping"=dword:00000001
"Publisher"=dword:00000001
"Spatial Analyst Pro"=dword:00000001
"Workflow Manager Pro"=dword:00000001
Per user, which isn't really acceptable, as we have to get IT do it for each person. We have requested the bug severity to be set to "High".
Have your TSA reference case