I’ve used Firstbeat’s ATHLETE product for quite a while. It was officially unsupported nearly a year ago.
The COACH function of it was great for giving a suggestion for the desired training effect from today’s exercise based on recent performances. It still worked perfectly well enough, even though it was unsupported.
However with recent changes to the FIT file spec, FB Athlete simply does not import many FIT files for me any more. Specifically ones that allow DEVELOPER data which, for example, includes POWER DATA from the STRYD CIQ field.
It didn’t work either with swim-based cached HR data but I was prepared to struggle through that one by using the awesome (but not free) fit repair tool. That’s my go-to tool for fixing anything. It does fix pretty much anything FIT-related but I just can’t face having to manually fix a third of my workouts before importing into SportTracks.
If you are in a similar position to me then the fit repair tool will solve your problems.