Sync failed on Android (failed to verify certificate: x509)

Hello,

I noticed today that my mobile app had trouble updating. continuously giving me this issue:

Sync failed: download object [siyuan/[...]/repo/main/refs/latest] failed: Get
 "https://siyuan-data.liuyun.io/siyuan/[...]/repo/main/refs/latest": tls: failed to 
verify certificate: x509: certificate signed by unknown authority 
(Provider: SiYuan) v3.8.9

I tried switching between data connection and wifi, disabling the DNS and the DDG tracking protection (none of which had given me prior issues) but the sync function is still casting the error.

Did something happen on the server's end? Is there a known troubleshooting way i can test?