Unsupported api version error

My checkout payment section spinner stays visible and spinning and does not allow card input. In devtools I can see a javascript error in snipcart.js and clicking through I find this detailed description of it:

“The HTTP resource that matches the request URI https://payment.snipcart.com/api/public/sessions with API version ‘2019-05-21’ does not support HTTP method ‘GET’”

Hi there,

It is normal for this endpoint to return that error when accessed via the GET HTTP method. It only supports POST calls, so loading it in your browser will not work.

To find the actual error that’s happening, please monitor the “Network” tab of your browser developer tools and look for any failing calls.

Cheers,