I am having the exact opposite problem .... I can not enable elevation corrections on my 310xt. If you can find a fix, I would be interested in hearing it.
I cannot enable elevation correction either. There is no setting on the Dashboard. If I go to the page for an activity, the button for enabling elevation corrections does nothing. The elevation gain and loss figures that are shown for my run on Saturday (using my Forerunner 620) are about 2,000' off!
This level of inaccuracy, plus the inability to use the elevation corrections from the maps is just unacceptable considering what this device costs.