I assume you tried turning the VPN off as a test. I would also try (with the VPN on) different VPN servers, and try a bunch and not just two or three.
EDIT: I'm also using a VPN and running the WireGuard protocol. I opened the Stocks application and it connected ok. Another idea to try, if you have a choice of protocols, is change the protocol and test.
What VPN provider are you using? Some offer content blocking through their DNS server. You could change the DNS server in the VPN configuration to a public one:
Cloudflare: 1.1.1.1, 1.0.0.1
Google: 8.8.8.8, 8.8.4.4
OpenDNS: 208.67.222.222, 208.67.220.220