The Proton VPN has worked flawlessly, however it should be pointed out that I have had a number of issues based around cloud based services either responding with a 403 or 500. These seem to relate to specific services which detect and deal with proxy related services with a service specific response. When disconnecting from the VPN the servers respond in an expected way.
I believe that this is VPN based and not Proton based. It seems some of those submitting reviews may have experienced this.