Hi,
I have got problem with the square checkout pop-up page that doesn’t open on the first attempt the majority of time. I get error 404. if customers refresh the page then it works and check out page successfully opens. Not all customers do that and when they get the error they simply decide not to proceed and I loose the business. I have created a new app and still getting this error. Sometime it goes through on the first attempt but majority of time it doesn’t. I have also tried regenerating new Access Token and still doesn’t work. Please advise how to fix the issue as it’s annoying.
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Which URL are you using? Is it the url or long_url. If your directing the customer right after the link is created you’ll want to use the long_url. 
Sorry. I don’t know what do you mean by Url or Long Url. I am using Booknetic appointment system and I have copied pasted the “Access Token” and Location ID that Square application is giving me into my booking system payment setting.
When you get this error, if you refresh the page does it load correctly? If so you’ll want to reach out to Booknetic. They should be using the long_url to redirect.
Correct. It loads when you refresh it. I will notify them.