I take it your box is not a Droidbox and you have not updated with one of the most recent OTA updates.
One of the issues with applying unofficial firmwares is it can kill or reduce functionality on the box.
Typically people, who have tried to update boxes running android 4.4 to android 5 lollipop on boxes running amlogic s8** series chips find that they have problems with wifi or remote not working after the update.
You provide little information on your box or what you have attempted to update with the new firmware so it is difficult to diagnose further.
My suggestion would be to contact the box supplier to see if they can provide you with an original firmware so you can reflash. Alternatively, you could check the Freaktab site for a compatible firmware although you will probably have to experiment as there is are many different firmwares for a particular chip.