Hi, I, together with some athletes I coach, recently joined. A few athletes, including my own historical data/workouts, pulled in perfectly, but not all.
I use a Garmin, so does most of my athletes. One uses a Polar.
I can’t recall what I did to get it in, but think during setup it was asked from me.
For Garmin historical data, you can request your entire history. This topic covers how to do it. No need to download the data, just copy the link from the mail.
For Polar, I’m not sure about historical data; I only use their HRM paired to Garmin devices and Zwift/IndieVelo.
I have been trying to track down the source of this problem with (some) new users. Please DM me links to the Garmin athletes with issues. I added lots of extra logging to try sort this out.
Actually looks like your athletes are getting current activities just not old ones. Garmin history is a bit hit and miss. They might come through otherwise use Gerald’s suggestion.