Can't checkout online

For the last three weeks I have constantly been unable to check out online. After choosing a delivery time and proceed to checkout I get an error message that an error in processing has occured. I cancelled my Walmart+ membership and now do all of my online grocery shopping at Publix. 

I use three laptops and three tablets and experience the same problem on all of them. 

Too bad that Walmartgrocery.com obviously isn't ready for primetime yet.