I just upgraded my phone and tablet to iOS 12. I have used the Earthmate app exclusively for many years. I have a number of tracks and waypoints that I can see and manage through the explore web portal. However, nothing shows now on my iOS 12 devices. I have reconnected and re-synced. App shows it has syced. But, no wapoints or tracks show. I create a new waypoint in the web portal, still no sync with the app. I can create a new waypoint in the app. It won't display in the app, but it does show up on the web portal. I have deleted the app, flushed everything known to man and reinstalled. No luck. Same problems. This has REALLY messed up my hunting season. I create tracks and waypoints on the web portal and sync to my Earthmate app as well as my Rhino 750, Fenix 5 and BaseCamp Windows app and between all these devices as they are used. The primary device is the app on my cell phone and I need it to work. Any ideas???
At a guess, this has something to do with the relatively new "collections". Updating the O/S may have deleted old data. Certainly, uninstalling and re-installing the app would do so. It should all re-synchronize. But in order to make that work, you have to get the collection thing right. Aaaaand, since collections don't seem to have been incorporated into the Earthmate app, I'm not sure what happens there.
There are now options on the Plans and Devices tab for managing collection syncing. You can select the collection(s) to be sync-d to the device. If this was working properly with Earthmate, I would THINK that this would apply to the app as well. The legacy "Library" collection is selected by default. However, there is also a warning that "Large collections may not sync." So if you have years of data, you may be out of luck.
There is also an option for setting the collection to which data generated on the device (for example, waypoints marked on the device in the field) will be added. At least on my account, my selection of the legacy "Library" collection will not stick.
Try going to the web app. Go into your library where you see your waypoints. Click on the sync icon. Make sure Earthmate Mobile All is checked. I had this same problem and was told by Garmin that the app was discontinued... ciq.forums.garmin.com/.../1421053.jpg