Depending on the VPN you use, it may have a fixed end address, or more likely, has rotating end points and IP addresses...
Some of those addresses and end points, will be on Netflix "black lists" of known VPN's - and therefore won't work.
Typically the default setup randomises the connection end points - and then it is pot luck whether it works or not.
I prefer to set a fixed end point, that I know works, and then change it when Netflix stops working....
It's an arms race, and it goes back and forth between Netflix (and other streaming services) and the VPN providers.