QuickBooks Online sync error: Invalid entity data. phone: Maximum length cannot be greater than 21 characters

Why the sync error occurs

This error occurs when a vendor with an entry in the phone number field is attempting to sync from QuickBooks online to Cashflow360℠, but the phone number is longer than 21 characters in QuickBooks Online.

How to fix the sync error

Edit the vendor's phone number in QuickBooks Online so it's 21 characters or less, and sync again.