What is wrong with my phone?
What does this error code mean?
The Samsung Galaxy Note 4 is a cellular smartphone that was released in October 2014. The Galaxy Note 4 Model Number is SM-N910, SM-N910A, SM-N910T, SM-N910V, or SM-N910R4 for American variants.
Seems like phone is in Download Mode... Just simply take out the battery and insert battery pack again and It should be working fine. if not Phone OS needs to be reinstalled.
Download Firmware from https://www.sammobile.com/firmwares/ and install Firmware.
hope this helps.