There are some LG Optimus G smartphone users who have been having problems or issues with not being able to change the manual setting to receive emails and may not be receiving emails to their phone
If your Sync setting is turned off, you will not be able to change the retrieve interval setting since it’s been disabled.
In order to “fix” it, follow the troubleshooting suggestion below:
Drag down from the very top of the screen to access your quick settings menu (QuickMemo, Sounds, Wi-Fi, NFC, Sync) The Sync setting must be “turned on”. This has to be on Blue in colour (in some cases) in order to change the retrieve settings.
Once the Sync button is turned “on” – go and re-open your email settings and you should have access to the change the retrieve interval from Manual to 15-minutes, 30-minutes, 1-hour, 2-hours, 4-hours and 8-hours.
LG cellphone issue: LG Optimus G, Troubleshooting, Un-clickable, won’t let me change or access settings.