VMware Update Managet (VUM) fail after upgrade

Sometimes after a vSphere upgrade Update Manager (VUM) can fail with the following error:

There was an error connecting VMware vSphere Update Manager - [vcenter.example.com:443]. Database temporarily unavailable or has network problems.

The easiest way is to reconfigure the VUM using the VMwareUpdateManagerUtility.exe utility installed in the VMware Update Manager program path (usually C:\Program Files (x86)\VMware\Infrastructure\Update Manager):

vum error

Then restart the VMware vSphere Update Manager service.