Seems like since the last update, not sure if it was Windows or MB Privacy, MS Store no longer works when VPN is on. Launches but keeps on saying that I am offline even when I am not, turning off VPN, MS Store starts working again. Let me know what information you may need to get this sorted out.
OS: Widows 10 Version 21H1 Build 19043.1288
VPN: Malwarebytes Privacy VPN Version 3.9.0.729
MS Store: Version 12107.1001.15.0
Server: Singapore
Auto Connect: Enabled
Tunnel Driver: Wintun
CPU: R5 3600
GPU: GTX 1080
Mobo: MSI MPG B550 Edge Wi-Fi
Bios: 1.72.
Left other settings as default. Doesn't matter which ISP I use (I got two different ISPs, yes).