As @msmaggie060 said, there have always been problems with some people requesting invoices.
For one thing, the option is not available at all on the app. Also, if any of the items in the cart have free shipping, immediate payment required, are on sale or have any sort of discount, the request total can't be used. Even if none of those reasons exist, the request total may not work. But according to eBay the cart up is working as it should.