Garmin changed the way the training effect/load is calculated and it is now calculated directly in Garmin Connect. See GPLama video about this new feature.
I emailed myself the RGT ride and uploaded the fit file to Garmin Connect and … well, training effect was not calculated. BUT there is workaround.
Use FitFile Tools, launch Device Changer and change the device in fit file to eg. Garmin Edge 830:
Save updated fit file and upload this file to Garmin Connect. After that you will see Training effect for that RGT ride. Training load is also calculated.