I use a VPN to connect for work, and have been having some macOS VPN adventures with my MacBook Pro. Mostly my problem was that, on occasion, the internet connectivity would not work, as I could connect to the VPN just fine, but any internet requests would just return with a failure.
The way I found to work around this issue was to go into the advanced settings for the VPN and hard code the DNS server of 18.104.22.168 in there. After doing that, it seemed to work much more solidly.
As a bonus tip, if you happen to use VMware Fusion on your Mac to run a Windows VM, I would also recommend going into the network adapter settings for your VM (all of them if you have more than one) by launching your VM and selecting Settings from the Virtual Machine menu, and select the Internet Sharing “Share with my Mac” setting instead of going directly to your Wi-Fi or Autodetect under Bridged Networking, or otherwise your VM will not communicate through the VPN you have running on your Mac at the same time.