PayPal Guest Checkout needs to be enabled for Bookings.

OK without any official response from Microsoft in either forum here or the suggestions forum, I did some more digging into API checkout options that might be causing this issue.  Here is one possible cause of the issue.

Documentation

https://www.paypal.com/fm/smarthelp/article/how-do-i-accept-credit-cards-with-express-checkout-using-the-guest-checkout-option-ts1623

• As long as SOLUTIONTYPE=Sole is passed in the SetExpressCheckout API, Guest Checkout will be enabled.

Have double-checked that this is not cookie or email address related during the checkout process, by making sure to clear all history & browser cache plus use email addresses not recognized as ones with associated existing PayPal accounts.  So there is no reason that PayPal should be forcing a signup option.

Checkout URL Construct (Microsoft Bookings)

https://www.paypal.com/checkoutnow?token=XXXXXXXXXXXXXX#/checkout/signup

This is almost certainly a problem with the way Microsoft Bookings is calling the PayPal checkout using the format .../checkout/signup where XXX is the token number generated during the payment API call.

Guest checkout with just a credit card NEVER works.  Please come on guys, this is hopefully an easy fix by modifying your payments checkout API call, otherwise this wonderful payment integration is of no value to our customers.  No one is going to signup for a PayPal account just to buy our service.

Thanks for the consideration of this fix, it is much appreciated.

Alastair