My embed iFrame does not work properly

Site URL: https://www.nickjewellery.com/stuller

The embedded iFrame is not working properly. 

The Quick Shops functionality is not working while embedded in Squarespace. A customer should be able to pick and choose a colour, size, shape etc of their order. This functionality does not work in Squarespace, but it works fine when accessing it directly ( https://nickjewellery.jewelershowcase.com/quickshops )

Any ideas?

Thanks !

p.s.

embedded iFrame code

<iframe style="width: 1px; min-width: 100%;" scrolling="yes" width="100%" height="1320px" frameborder="0" sandbox="allow-scripts allow-forms allow-same-origin" src="https://nickjewellery.jewelershowcase.com"></iframe>