Customer cannot add more than 5 products to cart

We have had several customers contact us complaining that when they try to add multiple products to their cart – that it just stalls out. I attempted myself, adding 5 products to my cart successfully, yet when trying to add more than the 5 – I see the wheel turning on the Add to Cart button and it will not add any further products. This is obviously costing us sales – I would appreciate any help!

Thank you!
Jessica

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