If you need to switch from one PayPal to another you need to temporarily downgrade your Mouseflow account to the Free Plan. You can do this by following the steps below:
Navigate to your Mouseflow Account Billing section here
Click "Change" on the right hand side, which will take you to the subscription selector.
Choose the Free Plan.
Click "Confirm Downgrade". You wont lose any data on your account by doing this.
Once the downgrade is complete, you can upgrade again using your preferred PayPal Account.