Dear Shalom,
Thank you for the clarification! You did not mention how you are trying to "synchronize" - iTunes or iCloud.
Anyway, I shall suggest that we try using iCloud because the features you mention can all work with iCloud.
Both devices should be charged nearly fully and connected to the internet (preferably Wi-Fi), and the Date & Time Settings are Set Automatically (Goto Settings > General > Date & Time > Set Automatically). Turn off any VPN, if using any. Quit all apps on both devices.
- If you use more than one Apple ID, verify that you are using the same Apple ID on both devices.
- Verify that iCloud is setup with same/similar settings turned ON on both devices, so that the features you want sync. Basically, on each device, to choose which items you’d like to sync across your devices, go to Settings -> (Your Name - Apple ID) -> iCloud and tap the toggles for the appropriate selections. Also, ensure the toggle is ON for iCloud Drive.
Read this for more details https://support.apple.com/en-us/HT208681#ios
If it is setup like that, iCloud should work and get your devices "synchronized".
If it does not work, try switching OFF iCloud and then try switching it ON again.
If that does not work, Restart iPhone and iPad and try again.
Let me know if this helps and if you need any more clarification and/or help!
Good Luck!