I have the same issue. What is the solution?
Update: my graphs are back! Checked between now and an hour ago, they’re back all of a sudden!
I have the same problem. The heart rate timeline will not display on Garman connect. In its place is “ Sync your device to see today’s timeline“. This happened once before and I had to delete the app off of my iPhone and delete all the data as well. I would prefer not to have to do that again. Please advise.