Nl80211:driver initialization failed | HOTSPOT with hostapd.

Question

I had no troubles setting up a hotspot for my nexus4 in ubuntu using hostapd.. But in Arch I am always getting this error:
sudo hostapd /etc/hostapd/hostapd.conf
Configuration file: /etc/hostapd/hostapd.conf
nl80211: Failed to set interface wlp8s0 into AP mode
nl80211 driver initialization failed.
I am currently using NetworkManager. I've tried to look for a solution on the forums.. but nothing has helped.
Also I don't get this error if I stop the NetworkManager.service but the hotspot doesn't seem to work properly then.
My /etc/hostapd/hostapd.conf :
ssid=YourWifiName
wpa_passphrase=Somepassphrase
interface=wlp8s0
bridge=br0
auth_algs=3
channel=7
driver=nl80211
hw_mode=g
logger_stdout=-1
logger_stdout_level=2
max_num_sta=5
rsn_pairwise=CCMP
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP CCMP
Please help me. I have only one wired connection available here.

Answer 1

I have started the hotspot building the hostapd myself.. my device lists the hotspot name.. but it can't connect to it.. it just saves the password and then nothing happens when I try to connect to the hotspot.
I did this:
After make for the hostapd.. I configured my hostapd.conf.. and then instead of  sudo hostapd /etc/hostapd/hostapd.conf in the script
#!/bin/bash
#Initial wifi interface configuration
ifconfig $1 up 10.0.0.1 netmask 255.255.255.0
sleep 2
###########Start dnsmasq, modify if required##########
if [ -z "$(ps -e | grep dnsmasq)" ]
then
dnsmasq
fi
#Enable NAT
iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables --table nat --delete-chain
iptables --table nat --append POSTROUTING --out-interface $2 -j MASQUERADE
iptables --append FORWARD --in-interface $1 -j ACCEPT
#Thanks to lorenzo
#Uncomment the line below if facing problems while sharing PPPoE, see lorenzo's comment for more details
#iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
sysctl -w net.ipv4.ip_forward=1
#start hostapd
./hostapd ./hostapd.conf 1> /dev/null
killall dnsmasq
I used ./hostapd ./hostapd-minimal.conf  ... because sudo hostapd /etc/hostapd/hostapd.conf still gives the nl80211 error...
What is stopping my device to connect to the hotspot it can see?
Note: I've used dnsmasq.