Following up on a similar thread that is now locked - it looks like ECG is taking an unreasonably long time to upload to Garmin Connect (web). I can see readings from a month ago but the one I took yesterday is still not there.
The measurement completed on the device and provided the results as well, I tapped "Done" at the end etc. It's been ~12h but no trace of the reading in Connect yet. This seems to started to happen recently, measurements taken a month ago showed up immediately as any other activity log.