The data stored in the app on your smartphone won’t be uploaded if your phone isn’t connected to the Internet . You can check the data pending to be sent from your Alert app to the cloud by going to Alert app>>More>>Settings>>Advanced Settings>>Alert Storage. If Alert Storage says "Nothing to upload " it means there is no data to be sent from your smartphone.
If there's a number along Alert Storage- it means there's data to be synced, so make sure to upload them - the process is automatic - just activate Internet connection on your smartphone (cellular data or WiFi connection - the latter is necessary if you've activated the option to upload data only via WiFi).
If Internet connection is active, but you’re still not able to upload data, force the app to close and reopen it again.
For iOS devices: How to force an app to close
For Android devices: How to force stop an app