I don't think this is a problem in Virtualmin Professional, but it is definitely a problem with the current GPL version (2.601).
Whenver a new version of Webmin (not Virtualmin) is released, including minor development updates, Virtualmin GPL requires it's configuration to be re-checked and refreshed. However, this isn't an obvious step, especially when Webmin is updated as an RPM. In my case, I have forgotten to do it a few times until a user has complained that they can no longer access Virtualmin. Then, when I finally access Virtualmin to check on it, I see it is sitting at this screen:
Virtualmin's configuration has not been checked since it was last updated. Click the button below to verify it now.
Hopefully, this has already been resolved in Virtualmin Professional and will trickle down to the GPL version.