First, let's clarify what data is not being synced in your new PC; are you referring bookmarks, passwords, tabs, pinboards? If you expect to see your old speed dials in your new PC, you should be able to see them under opera://bookmarks/. Keep in mind that Opera sync won't replace Speed Dials in your new PC and new installation.

If your bookmarks and speed dials are not in opera://bookmarks/ in your new device follow these steps;

1- See if you selected "sync everything" enabled in your previous PC. Then go to https://auth.opera.com/ and check your synced data again on your old pc. Make sure you are using the same Opera account for both new and old device.
2- Check your encryption option and see whether you use Opera Credentials or your own passphase in your old device. You can see this Sync -> Advanced sync settings -> Encryption options. Try changing the setting and check auth.opera.com again after a few minutes.
3- Once you see your old pc data is synced in server, then go to Opera One in your new device and login again.
4- If you don't see any synced data in auth.opera, try using a VPN that works in your country and change the location in your old PC. Then check https://auth.opera.com/ again.
5- In case you finally manage to sync your old pc in server, reinstall Opera One while the VPN is on.
6- Still no luck? Install V94 developer in your new device and see if sync works between your devices.

If none of these worked, see this article and let us know the outcome.