No booking emails being received by site admins when using Stripe

My client has a multi-site network and, until two weeks ago, each of the site admins received two emails when a customer booked with Stripe; one from the site and the other from Stripe. Now, although the booking appears in the back-end there are no emails either to the admin or the customer. This does not happen for PayPal bookings – only those made using Stripe. Any thoughts?