Payment Form NOT Showing Front End

Hi
I have two websites and both have the same error - page not showing on front end - one with a 404 error and the second with the error below.
Both were working perfectly until update. Is there a fix? Or something I need to change?
Best regards
Heather   

 

Could cause by PHP upgrade somehow. Please submit a support ticket sending us super user account of your site and link to the page which we can see the error

We are going to check to see why the issue happens and get it sorted

Regards,

Tuan

Update: For some reasons, a none core payment plugin (Stripe Checkout) was lost on the site and it causes the error

I just installed the payment plugin and the error is gone now

Tuan