Hey Guys / Girls!

I've recently moved back to Kali after using Parrot Sec for a few months and have come across a very strange issue.
When I was using Kali before, I never had any issues with my TPLink Archer USB (this also worked fine on Parrot).

But since coming back to Kali (after around 8 months away) my Archer will no longer allow monitor mode.

Kali Version: 4.19.0-kali5-amd64

USB Adapter: Archer T9UH AC1900 (EU/1.0)

I've tried everything from reinstalling drivers (from TPLink's website using the documentation that they provide).
I've also attempted to install from here (https://github.com/aircrack-ng/rtl8812au)

When attempting to switch to monitor mode by running the following, the output of 'iwconfig' does not change
Code:
ifconfig wlan1 down & iwconfig wlan1 mode monitor
Code:
root@powerKali:~# iwconfig
eth0      no wireless extensions.

wlan1     unassociated  Nickname:"<WIFI@REALTEK>"
          Mode:Managed  Frequency=2.412 GHz  Access Point: Not-Associated   
          Sensitivity:0/0  
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=0/100  Signal level=0 dBm  Noise level=0 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

wlan0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on
I'm pretty familiar with Kali now and this just seems to confuse me.

EDIT: 'airmon-ng start wlan1' results in the below

Code:
root@powerKali:~# airmon-ng start wlan1


PHY    Interface    Driver        Chipset

phy0    wlan0        iwlwifi        Intel Corporation Wireless-AC 9560 [Jefferson Peak] (rev 10)
phy3    wlan1        rtl8814au    TP-Link 802.11ac NIC


ERROR adding monitor mode interface: command failed: Operation not supported (-95)
Any help would be great!