Is this you? https://hdyc.neis-one.org/?InsertUser I think the problem is on your end, I can see your chart. Maybe you block some script required to draw that? It's drawn by the frontend.
I'm using Firefox with strict protection policy with Ublock Origin on Linux, so it's not a general Firefox thing, I would consult the browser console, or maybe check if it's still not visible in a private window and without addons.