I was able to upload files exported from Rouvy in .tcx format with no issues. I haven't used my trainer n a couple months and I've used it twice in the last few days and neither of the output files will load into Connect. It will upload the file if I output it as a .fit file.
I think you may have found your way into the wrong forum for this report. This is for the Connect IQ Software Development Kit used to make 3rd party content for our devices. You're probably looking for the Garmin Connect website forum. I'm moving this thread over there so you can get the help you are needing.