Contacts not syncing on iOS 13.1
Here's a fix for disappearing contacts in iOS 13.1 on iPhone 7 plus:

It turns out the issue isn't with iCloud, it's with a new default in iOS 13.1.


Go to your Contacts app.
Press (+) from the top right and add new contact.
Save your new contact.


Now wait for ~1 minute and your contacts will appear again in your phone.

Probably the problem is in the sync functions for the first run.