Two summary fields to one table

I have three tables:
Trucks
Equipment
Scanned Assets

In the trucks table, I have a summary field - Distinct Count - Scan Dates in the last 30 days
The summary field works fine and the number is correct.
I have the same field in the Equipment table, set up exactly as the trucks, the field doesn't work. Everything is zero.
The scanned assets table shows a date and the info for the truck/equipment every time they are scanned. (Imported from a csv)
Report links for both tables show all scans in 30 days but I need a distinct count for each table since they are tracked separately. 
Why would one work and the other not? Both use truck/equipment number as primary key, tables are nearly identical. 
Thank you


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Steven Pearson
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