Error on adding to checkout

[JoeMitchell]

Hi,  Received this error from the storefront API:

Error: Internal error. Looks like something went wrong on our end.
Request ID: 5b1b8c3e-a51b-4ceb-9701-8edf18ece7e1 (include this in support requests).

Couldn't find another way than here to contact support so please can it be looked into?

Thanks, 

Joe Mitchell