When I try to set an ImageButton's image property the request always fails, why is this?

Hello. I am trying to set an image button's image. However, when I give it a string of

"rbxassetid://00000000" with the zeroes replaced with the actual id of the decal it just says that the request failed. I went into further detail and actually found out how to get this decal, and downloaded it from my browser.

This script is a server script.

I also tried this outside of roblox studio ingame, and this did not help. I additionally tried changing the string to the url of the decal in roblox library, to no avail.

Why did the request fail?

Code:

ToBeDisplayedGuis[y].Image = "rbxassetid://"..ToBeDisplayed[y].ShopInfo.ImageId.Value

the ToBeDisplayed[y].ShopInfo.ImageId.Value is the id of the decal

Thanks in advance