Inventory System Bug

I’m using a Free Inventory System Backend to make an inventory system, the link is here: On spawn, I have been adding 4 stacks of Meat Chunks. These work fine, I can add and remove them just fine. But whenever I add any Meat Chunks after this it doesn’t work. It shows up in my inventory just fine, with the correct quantity and such, it detects its there because whenever I hover over it the background changes, but I cannot add or remove it from my inventory. I tried doing the same thing in the example save it gives you, by setting it up so that whenever I press ‘1’, it adds a stack of Meat Chunks. This also does not work.

I have tried a handful of different things, I suspect it may be a problem with getting data from the index, but I am not sure.

Any help will be greatly appreciated! Thanks.