The health check option proceeds apace through all its checks until it gets to the last one when it says something is not right and it cannot find server.
Am I right in assuming this is because the program cannot detect VPN's other than piriform's own?
That was a known issue in v5.64 and has been fixed in v5.65 which was released yesterday.
https://community.ccleaner.com/topic/57660-ccleaner-v5657632/?tab=comments#comment-317202
It was actually connecting to the server but displaying the wrong message when Health Check found that no software needed to be updated.
See here for more details:
If you are still seeing this with v5.65 then please post back, the devs would be interested to find out why.