Rancher started work extremely slow


I just started to use Rancher 2.6.5
Didn’t monitor and touched it for a week and users started to report slowness. Actually it’s impossible to work with it at all.

Most of the kubectl commands return errors like this:

Unable to connect to the server: net/http: request canceled (Client.Timeout exceeded while awaiting headers)

Main dashboard is not shown from UI – just loading , but UI allows to display nodes, pods, namespaces, etc.
Longhorn, Grafana, Prometheus are not opened in a new windows – just loading is started.

What is the cause can be this issue? What you can suggest to check?

Thank you