I emailed a track to myself so I could view it in Google Maps, but when I click the link, my track is no longer available.

The link to view tracks in Google Maps on your PC or Mac expires one month after the email was sent. The date of expiration is in the email. You can always use the attached GPX or KML files to display your track again. Once displayed in Google Maps we suggest using “Save to My Maps” to save for future use.