I have a 310xt which connects to my PC without problems but will not connect to garmin connect
I installed garmin express but still does not work
Your 310XT doesn't connect to Garmin Connect at all. The provided software (Garmin Express or ANT Agent) connects to your device. If properly configured, that software will download activities from your 310XT to your computer. Again, if properly configured, that software will upload your activity data to Garmin Connect.
If your activity data is not appearing in Garmin Connect, but you see that the data is being transferred off of your 310XT, then you most likely configuration problem. Often the simplest fix is to un-pair your 310XT and then re-pair it. How you do this depends on which software you are using, but you should be able to figure it out without many clicks.
Travis