Why is the receiver not syncing with drone?

I tried changing the batteries and recharging the drone battery. When I turn the receiver on, the green light is blinking fast and then after moving throttle up and the down it starts to blink slowly but never stops blinking. What is the reason for not pairing?

crwdns2893858:0crwdne2893858:0 crwdns2893862:0crwdne2893862:0

crwdns2894050:0crwdne2894050:0

crwdns2889612:0crwdne2889612:0 0
crwdns2892346:0crwdne2892346:0