At some point the Paypal Payment Option stopped working for invoices on my account.
I made a test invoice this morning and when I clicked on paying with Paypal I get the following screen and message
That message is normally displayed if the software cant link to your PayPal account.
Open Account Settings > All Settings > > Integrations Tab > Online Payment Integrations and select PayPal down the left check the “PayPal Registered Email” is correct.