I have fixed one issue, where License manager instance (8.3) Enterprise - > Oracle option was failing throwing error "page cannot be displayed". LM portal crashes and need to login again to LM. Rest all TABs are working fine in License manager Portal.
After lot of time invested in troubleshooting the error, noting was working. I had disabled the Auto-discovery and removed the ORG structure (AD imported). This fix has worked and Oracle TAB started working fine.
ORG Structure was imported from Customer Active Directory. Some auto-connect rules were applied on basis of custom values.