MY CONTACTS ARE NOT SYNCING

1. Find whichever device has the most up to date contacts on i.e. your phone.
2. turn off contacts in iCloud on your other devices. (NOT ON YOUR MOST UP TO DATE DEVICE)
3. when it asks do you want to keep them, say no and let it delete them
4. on your iPhone, turn off contacts in iCloud, but when it says do you want to keep them on your phone say YES
5. leave it for around 10 minutes so your contacts in the cloud are cleared
6. then turn contacts for iCloud back on on your phone, leave it 10 minutes so it syncs back to the cloud
7. turn contacts for iCloud back on on your other devices

this process resets iCloud contacts and any other item as well i.e. keychain, bookmarks etc etc.

As per this article https://support.apple.com/en-gb/guide/iphone/iph875319a3a/13.0/ios/13.0

1. Connect iPhone and your computer using USB.
2. In the Finder sidebar on your Mac, select your iPhone.
3. Note: To use the Finder to sync content, macOS Catalina is required. With earlier versions of macOS, use iTunes to sync with your Mac.

You are using Mac OS Catalina 10.15 , and what are the versions of iPhone / iPad if they are of old version use iTunes to sync the contacts .

See the article https://support.apple.com/en-in/guide/itunes/itns5ecc4d98/12.9/mac/10.14

Read this also https://support.apple.com/en-in/guide/mac-help/mchlf24d4e49/10.15/mac/10.15