I downloaded version 3.4.2.8 and I can confirm that the issue still persists. Every airport I try continues to give me a no parking warning, even ones I know only have one flight assigned to them.
My procedure:
Open AIFP3.exe, allow changes to my computer, click "Files", click "Load Traffic File (.bgl)", click trafficAircraft.bgl file in D:\SanDiskSecureAccess\Official\OneStore\fs-base-ai-traffic\scenery\world\traffic, click "Open", click "Bulk Traffic", click "Traffic and Parking Analyzer", click on any airport in the list (KFJK in my latest attempt), click "Analyze Parking", dialog box pops up with title "AIFP3" and message "No parking available at "(airport)"". Checking "Access All Drives" before running this procedure again doesn't change anything in this version either.
One thing I noticed is that after clicking trafficAircraft.bgl in the Traffic and Parking Analyzer's Selected Traffic Files area, the error message that pops up when I try to Analyze Parking changes to "No parking at (airport) required".
Another is that in a brief amount of time I was able to get version 3.4.2.5 to List Parking at Selected Airport, a lot of the parking spots had their radii listed as 0.0 meters Only a handful had the correct size listed. Could the Traffic and Parking Analyzer be mistakenly reading them ALL as 0.0 meters and thus thinking that there's no parking available? Or that the airport scenery files in question are corrupt, or located somewhere the Traffic and Parking Analyzer isn't looking for them?