Latest branch as of https://github.com/FluxionNetwork/fluxion/commit/5522c85e7170cc2c373ff9bce5d897ad62ee53da
Kali 2017.1
realtek-rtl88xxau-dkms
Tried wlan0 and wlan1, both support injection
x@ghost:~/fluxion$ sudo aireplay-ng -9 wlan0
19:12:11 Trying broadcast probe requests...
19:12:11 Injection is working!
19:12:13 Found 1 AP
19:12:13 Trying directed probe requests...
19:12:13 50:C7:BA:1C:01:5A - channel: 1 - 'TP-LINK_Smart Plug_015F'
19:12:13 Ping (min/avg/max): 2.403ms/7.006ms/33.810ms Power: -41.00
19:12:13 30/30: 100%

After selecting 2, then all channels, WIFI Monitor never shows any clients. But selecting the integrated wifi card wlan1, it will fill in the results no problem. But I need wlan0, my new USB card.
WIFI LIST
ID MAC CHAN SECU PWR ESSID
(*) Active clients
Select target. For rescan type r
[deltaxflux@fluxion]-[~]
Here's running it in debug mode:
[~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~]
[ ]
[ FLUXION 2 < Fluxion Is The Future > ]
[ ]
[~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~]
PHY Interface Driver Chipset
ethtool failed...
Only mac80211 devices on kernel 2.6.33 or higher are officially supported by airmon-ng.
mon0, Select an interface
[1] wlan1 Intel 4965/5xxx/6xxx/1xxx iwlwifi
[2] wlan0 Unknown 8812au
[3] mon0 Unknown
Have also tried to install 5.1.5 https://github.com/diederikdehaas/rtl8812AU/issues/63#issuecomment-302216460
Must be some bug/incompatiblity with the bundled airmon.
Can you, please, execute the file lib/airmon/airmon.sh bundled with airmon and post the results here.
Also execute airmon-ng that comes with aircrack from your distribution and post the output from there as well.
Thank you.
@strasharo I will modify the interface function so it is comparible with the latest airmon version shipped with aircrack.
@strasharo I am not the OP but using exactly the same Hard- & Software setup and ran into the same problem. I executed lib/airmon/airmon.sh and airmon-ng. Here is the output:

Are you able to bring it up in monitor mode using airmon-ng? How do you flip it to monitor usually?
Sorry I don't have access to the laptop right now to test. I will have it tomorrow
I usually flip to monitor mode using "iwconfig wlan0 mode monitor":

the "airodump-ng wlan0" command is working fine after that and the second "iwconfig" command shows the card is in monitor mode
I can not start monitor mode via airmon-ng:

When I run "airmon-ng check kill" and "airmon-ng start wlan0" again I keep getting the same output
@Geczy do you use an other way to put the card into monitor mode?
I was getting the same issues as you in putting my card into monitor mode. For now I am using https://github.com/wifiphisher/wifiphisher which uses both of my wlan0 and wlan1, but I don't think it's the optimal solution...It's not utilizing the full potential of my new wifi card
I opened a new issue at aircrack-ng fin case that this problem is caused by airmon-ng:
https://github.com/aircrack-ng/aircrack-ng/issues/134
Here's what you requested @strasharo
Can you, please, execute the file lib/airmon/airmon.sh bundled with airmon and post the results here.
Also execute airmon-ng that comes with aircrack from your distribution and post the output from there as well.

Install drivers probertly. This is not a fluxion issue
any update how fix this method ,i have same issue like this alfa awus036ACH not support for Airmon-ng
I'm doing this :
Ifconfig wlan1 down
Iwconfig wlan1 mode monitor
Ifconfig wlan1 up
Nothing happens n that's still doesnt work with that
Well you don't have any basic understanding of wireless cards.
That wasn't very nice
I just turned off my wifi at top right corner in the drop down arrow..and it worked started showing me wifi networks on qifi monitor.