Consider the following before updating or switching your PayPal account:
1. Your PayPal needs to be verified.
If your account is not verified, you will see the message "unverified by PayPal".
PayPal can only be used on one account.
2. If this is not the case, you will receive the message "someone's already using that payment method"
From the Dashboard, select the Menu icon (top right corner of your screen) → Profile Settings→ Payment → Change Payment Method
From Dashboard, select settings → tab payments → Change Payment method