Authentication failed, Update Manager server could not be contacted

Today I tried to open the Update Manager and got the following error:

Authentication failed, Update Manager server could not be contacted

When searching the VMware KB I found the following article: https://kb.vmware.com/s/article/60436 But I already had the mentioned version installed.

A restart of the Update Manager service or login/logoff on the HTML5 UI didn’t fix the issue, as described in: https://communities.vmware.com/t5/Update-Manager-Discussions/VUM-failed-to-authenticate/m-p/2751225

At the end I was able to fix the issue by restarting the HTML5 UI service as well, with:

service-control --stop vsphere-ui; service-control --start vsphere-ui