When trying to configure PayPal Express Checkout in Chargebee, did you see an error saying "Sorry, we couldn't find that page. Maybe it was moved, or you accidentally mistyped the URL"? This error indicates that you're using a theme which is not compatible with PayPal Express Checkout.
PayPal Express Checkout works only with the Minimal, Elegant or Inspire themes. It does not work with Chargebee's Rhapsody theme. In case you're using the Rhapsody theme, please change it at Settings > Hosted Pages Settings > Themes and then try configuring PayPal Express Checkout. This applies for GoCardless and Amazon Payments as well.