I have both the "cloud" version of Power BI Desktop and the Report Server version of Desktop and the sparklines option is only present in the "cloud" version. Sparklines are currently a preview feature and neither Report Server or Power BI Desktop for Report Server support using preview features.
So unfortunately the answer here is that you will need to remove the sparklines from your tables since they are not currently supported by Report Server. Hopefully this feature will be out of preview before the May release so you should be able to add them back then (although I don't recall seeing an official timeline for sparklines, I'm just speculating)
My only thought about how this happened is that someone accidentally edited this particular report with the wrong version of Power BI and added the sparklines from there. And since this is a preview feature which is in active development the server release is probably a few days different to the desktop release and is missing some fixes that made it into desktop.