Size Charts not showing, but enabling multi size charts appears to make it work

Hi, when clicking on a size chart nothing appears, it was previously showing a size chart that I had deleted and was in the bin. I emptied the bin now no chart shows despite the product tags matching a item (it also does not show if I actually choose the product).

I have discovered that enabling the multi size chart option does make it appear, this is far from ideal, please assits.

Thanks.