For any problems with LED Blinker check this:
Please check if notification light is enabled under Android settings - Display and if ledblinker has Show notifications enabled under app Manager.
Disable any lock screen widgets or notification apps or other led apps!
Check if there is an option to allow third party apps to use/change led light.
Disable silent mode for samsung 5.0.x Firmware. (bug no led in silent mode)
Otherwise uninstall, restart and install again.
BTW: I am the Developer of LED Blinker Notifications!