Usually when you reinstall your mobile app custom network needs to be readded. To read your custom network please follow these steps:
1. In the Settings click Networks
2. Click Add Network
3. Fill in custom Network RPC parameters then click Add
Please make sure the network details are accurate. After you add the network it will show as an extra choice in Settings > Networks.
If you are using Sync with the extension option it won't sync you would still need to add it manually.