I too am a long time user and I too have these problems specifically when using my VPN.
My VPN is Ivacy and I regularly connect through UK servers (I am UK resident) as well as Ireland, Denmark - it makes no difference. When I am connected through my VPN I cannot access certain Ccleaner functions ( software updating, security checks..etc) as basically Ccleaner seems to be suggesting that I'm not connected to the internet. If I shut down my VPN the problem is instantly resolved.
The problem is clearly with Ccleaner itself.