So I guess that didn't work?
Is the app able to sync at all when your phone is connected through the VPN?
Just the "baseline", "does it work at all"?
( there are old posts with users saying that Aqua's mail sync through a VPN doesn't work, and back then, I tried a bunch of different apps with a top-rated Android VPN and about half the network-oriented things on my phone stopped working, not just Aqua )