The attached file is a Zwift workout I just completed. It did not auto sync to Garmin Connect and manual sync produces a non-descriptive error message.
This has been an ongoing problem for several weeks now. About 60% of rides from Zwift sync fine, but 40% fail. A 40% fail rate is absurdly unacceptable, made worse by an error message that tells me absolutely nothing about the problem - if it is something I'm doing, a way to fix it, etc.
I have tried the tools available here with no success as well: https://www.fitfiletools.com/#/top