Garmin only calculates training load and other values for activities from Garmin devices, and select third parties (it’s a handful - I think 7?). Garmin will not calculate from ELEMNT devices.
Garmin will update training load IF you have an Edge device for third party rides uploaded to Garmin Connect. It will update if you use a Garmin device to record the activity. It looks like you have a ForeRunner. Don’t know if that device has the capability of updating training load.
Forerunner should provide training load but maybe not if you’re using it in this way. Sounds like you’re using it as a sensor for the element rather than recording the activity using the Forerunner as the device? Is that correct?
To get training load w your setup, you may need to do something funky like record two activities, one with your fr (for hr only) and one w element for the other parameters. But that seems like a lot of hassle.