I just encountered the same issue:
Clients on Wifi cannot see eachother (cannot ping eachother), even tough AP isolation was disabled.
Strange enough, clients from LAN could reach Wifi clients.
All of that happend, after I setup a VPN. Even when the VPN was turned off.
That behaviour is a bug in the software after V 4.xxx, obviously there is no fix for it. but I found a workaround:
First: Find out, if that is your issue: On the impacted client do a ping and look, if there is a arp entry (arp -a), if not: the bug hit you.
I added this script into the LUCI local startup (System→Startup→Local Startup) directly in lines before the “exit 0”
# --- Workaround Flint3 WLAN-ARP-Bug ---
sleep 15
for i in /proc/sys/net/ipv4/conf/*; do
[ -d "$i" ] || continue
IFACE="$(basename "$i")"
case "$IFACE" in
phy*-ap* | wlan*)
echo 1 > "$i/proxy_arp" 2>/dev/null
;;
esac
done
# --- End Workaround ---
It will configure proxy arp at every reboot. After reboot you will see the proper arp entry, and the connectivity is restored.
Regards
Michael