I'm using Magento 2.3. The Paypal express button on the product page has worked perfectly up till last week when for no apparent reason the pop-up Paypal payment window stopped appearing and instead a message appeared across the top of the product page asking the customer to sign in. It doesn't specify sign in to what! I have switched off the Add Paypal Button to Product Page option and all other Paypal Buttons work fine. Switched back on the Product Page button and now that works fine. This is the second time this has happened. Am I going to have to check every few hours that the product page button is working???????
