If you saw your tile streaming on your app for the duration of your workout but did not refresh your home feed before you removed your belt, you disconnected too soon. Put your belt back on and tap My Tile on the app. You will receive a message saying "receiving data from belt." Once completed, tap Home on the navigation bar and pull down to refresh.
If you were also streaming at a Myzone-enabled gym, their system is likely offline. Please refer to this article.
If that does not help, there could be a couple of reasons for potential data loss:
Poor internet service
If you plan to earn your MEPs in the mountains, forest, or other remote settings with poor internet service, store your data and upload your workout later. Here’s why: your belt sends your workout to your phone via Bluetooth connection. Your phone then transmits it to your account using the internet. If connection is poor, your phone may push it out, but the weak connection could drop it before it lands on your account. To prevent this, put your phone in airplane mode. You can keep tabs on your zone and know that your data is safely stored in your phone until you get back to a place with stable internet service.
Streaming to 3rd Party Devices (MZ-1 and MZ-3 only):
The MZ-1 and MZ-3 are single-channel Bluetooth devices. This means they can send data to just one platform at a time. This means if you connect your device to a Peloton bike, Garmin watch or Strava, to name some examples, and then open Myzone, there is a chance that your data will be sent to the other device/app. This can be a tricky problem, as it may not happen every single time, but there is always a chance that it could. As such, if you have an MZ-1 or MZ-3 and enjoy using other trackers, no problem! Just keep Myzone closed, viewing your heart rate on the other display, and then upload once you have closed it out or turned it off.
If you did not see your tile on the My Tile screen and do not hear it activate, please refer to these belt troubleshooting guides: