Fatal error

I have set up subscription payments via 3 buttons on the home page of the site that takes you to a stripe payment. I have tried and tested and it worked. No it seems to work everynow and then.

The user gets taken to the payment then diverts to a page saying ‘critcal error’ if i creat a new sectret key it works than after a while gives the same error.

The page I need help with: [log in to see the link]