On touch devices there are no hover over tool-tips displayed, as hover over is not an possible action. Since you are using a hybrid device it sounds as if it is likely that the "wrong" action is picked up, and the tooltips are hence not shown. What kind of device and operating system are you using?
I have laptop with touch support and tool tips in combo charts didn't work. I spent a lot of time to find solution and at the end it was so simple - switching touch screen mode in Qlik Sense to Off which was automatically turned On. Hope this helps.