Error Msg "There's something not quite right in the URL"

[LowStarStudio]

I have a customer that went to check out an order and could not. The error message they got was: "there's something not quite right in the URL. Please check for any errors in the address bar and try again." 

Looks like the customer is purchasing through the Etsy app. 

[ChristmasIsLove]

They might have an outdated version of the app. They can uninstall and reinstall to see if that helps.