Why is Google blocking my merchant center account due to a checkout error?

[mnijhuiss]

So our merchant center account got blocked and Google states that this is because our checkout process does not work. 

When trying to checkout on our store everything works perfectly.

After communicating with Google About this issue they state that they encounter this error: Parameter Missing or Invalid: Required parameter missing or invalid: items

You can check it here: https://nijhuismeubels.nl/cart/add
I'm aware that this link is invalid and should not be generated bij our store. 

However, since we can't reproduce the error the Theme support of 

[EmmanuelFlossie]

All items sold online, must have the ability to be bought online. Unfortunately you seem to offer quotations only. Which is not an acceptable buying method.

Ensure all items can be bought online, with at least the ability to pay with credit and debit card upon checking out.

[mnijhuiss]

Thanks for taking the time to look into this. It's highly appreciated. However we only have 5 products on which we offer quotations. 
All the other products are available to buy directly online: https://nijhuismeubels.nl/collections/rechthoekige-eettafels?sort_by=price-descending

[EmmanuelFlossie]

In that case, make sure you only submit products that can be bought online. Google does not allow products to be listed for quotations only.

Based on the info you provided, it seems Google tested a product that is not available for online sale.

You can check what products you submitted by going to Google Merchatn Center > Products > All Products.