If you were hoping to stop by one of Amazon’s new new checkoutless, cashier-free convenience stores soon, you’ll have to put that plan on hold: A new report says the company isn’t quite ready to open Amazon Go to the public due to technical difficulties.

According to insiders cited by The Wall Street Journal, Amazon had originally planned to publicly open the new store by the end of this month, after a beta test for employees. Although the sources didn’t say how long Amazon will delay the opening, the company said in the past that the concept would debut sometime this year.

For the time being, the company has to smooth out issues that have popped up with the technology it uses to provide the cashless experience. Customers won’t have to wait in lines to check out, but will instead be automatically charged when they leave the store through an app that knows what items they’ve picked up while shopping.

However, keeping track of shoppers in the store is no mean feat, with sources telling the WSJ that Amazon is having a hard time tracking more than 20 customers at the same time. It’s also finding it tricky to monitor if an item moves from its specific position on the shelf.

If there are only a few people in the store moving kind of slowly, everything works great, the insiders said, but that’s not ideal for the store full of shoppers Amazon has in mind. For now, Amazon will need to have human staff on hand to make sure everything is working as it should.

The company didn’t comment on the WSJ’s report.

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