Hi Michael,
In the events report do the events show as zero, or only when added to the eVar report? Per the documentation here:
"Processing rules cannot read eVar values from the product list. eVars used by processing rules must be populated directly on the page (for example s.eVar1="news") or by using a processing rule earlier in the processing order."
If this is a product variable syntax the processing rule wouldn't work. The eVar would need to either be set on the image request, or implemented by a processing rule earlier in the order to set the eVar. I think in this case that is the most likely cause of the issue.
-Tacia