Interesting problem - here’s what I think is going on. Your card measure works on the main page because no additional context is being imposed on the global cumulative calculation. However, in the tooltip, when you hover over the visual, because you’ve used ALLSELECTED, it is also imposing the month context from the bar chart.
However, before fixing this I wanted to question whether a report tooltip is really the right mechanism here for providing additional detail? The problem with report tooltips is that you can’t interact with them, and given that you have scrollbars and tables that don’t fit the space in your tooltip, that’s going to be a problem.
My recommendation would be to use a drillthrough instead of a report tooltip to explore the details. On that drillthrough page I would synch the slicers from the main page (you can decide whether you want to display or hide them - it doesn’t matter from the calculation standpoint). Once you synch the slicers, you can remove the ALLSELECTED from your cumulative measure and then tailor the measure specifically for that page - i.e., using REMOVEFILTERS on Month&Year to keep it from imposing the monthly context on the cumulative calculation.
I hope that’s helpful.
- Brian