I've found that I can open some FIT files but none from Garmin. I suspect Garmin has added something that doesn't agree with TopoFusion. Maybe just tags or whatever that TF doesn't recognize but should\could just ignore? I'd be happy to send an example file or help in any way I can with resolving the issue.
Here's the error message I get from TopoFusion: Error reading file: (full path\filename).
