Failed to load resource: the server responded with a status of 500 ()

I can not seem to get past the checkout form! I get an error as if I had not filled in a required field but I have. in the console i have this:

Failed to load resource: the server responded with a status of 500 ()
2mailchimp-woocommerce-public.min.js?ver=2.5.4:47 mailchimp.handle_billing_email.request.success {"success":true,"email":"[email protected]","previous":null,"cart":{"6b283b8c9aa9dcada9edf49818d31937":{"key":"6b283b8c9aa9dcada9edf49818d31937","product_id":21547,"variation_id":0,"variation":[],"quantity":1,"data_hash":"b5c1d5ca8bae6d4896cf1807cdf763f0","line_tax_data":{"subtotal":{"1":2.100000000000000088817841970012523233890533447265625},"total":{"1":0.0023999999999999997897515147116109801572747528553009033203125}},"line_subtotal":35,"line_subtotal_tax":2.100000000000000088817841970012523233890533447265625,"line_total":0.040000000000000000832667268468867405317723751068115234375,"line_tax":0}}}
/?wc-ajax=checkout:1 
        
Not sure what is wrong, but everything was fine a week ago and I have not installed anything new.

Any help appreciated 
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1 
        
      
        
        
      
        
      
       
        
       Failed to load resource: the server responded with a status of 500 ()
/?wc-ajax=checkout:1

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