TimeTree may not be able to send you notifications due to restrictions from your device. In addition, widgets might not display right due to the battery-saving settings.
Check the following settings
- Huawei: The settings depend on the model number of your device, please see this help page: Unable to receive notifications from third-party apps - Huawei Support - English
- Asus: "Android phone Settings" -> "Power management" -> "Auto-start manager" -> DOWNLOADED page -> select 'Allow' for TimeTree.