1. What is the issue? Please be detailed.
I have two smartphones connected to the same Central project (an instance hosted on a Debian server). The forms are accessible and synchronized on one Android 8.0 smartphone, but synchronization fails on the other device running Android 16.
3. What have you tried to fix the issue?
I recently realized that the problem stems from using a VPN (Surfshark) on my Android 16 smartphone. When I disable the VPN, access to the server works perfectly. Do you have any idea what settings I need to adjust to access the server using my VPN?
I’m guessing you’re using ODK Collect on these devices? Collect is able to access servers via a VPN (the VPN is handled by the system itself), but the server must be accessible through that VPN and the server must accept connections from the VPN. Have you tested that you’re able to log in to or access Central’s web interface using that VPN?
I agree with @seadowg that enabling Surfshark on your Android 16 device and trying to access Central via its URL and via its IP is likely to give you some useful information.
Some other things you could try on Android 16 with Surfshark enabled:
- Disable Private DNS in Android settings
- Switch Surfshark to OpenVPN TCP
- Disable IPv6 in Surfshark