I am also having issues with whatsapp and two M9's

issues:

on iphone-only:              it permanently shows 'connecting' and messaging in the background doesn't work.
On android and iphone: voice and video calling don't work.

I tried:
turning beamforming and antivirus off, switching AP between router modes
 

Please provide some help how to solve this issue

Thank you

home-network layout:
In NL ISP = t-mobile, router provided by ISP as gateway and mesh for wifi.

| = wired connection
'' = wireless
               TV     XBOX                          RaspberryPI
                 |         |                                         |
Internet - {ISP ROUTER} - {DECO1}''''''{DECO2} '''''''''' [iphone's, android's, laptops]

@maxideco Hi! I had the same issue some months ago on a Deco X20 3-pack. After a recent firmware update on the Decos, Whatsapp is working fine on the iPhones and the iOS updates are also working. 

I don't know if the firmware is different between each Deco model.

I have the antivirus off, Fast Roaming Disabled, Beamforming Enabled, IPv4 Dynamic IP, IPv6 Disabled, QoS in standard mode.

I hope this works!

@MarkN @TP-Link_Deco 

!!Solved!!

between Router and AP2 I had a switch that i forgot to mention.

I replaced this switch with a new one and since then everything works like a charm.

=======

Is there a solution already??

I have (2x) M9 in AP mode and experience the same issue with one of mine deco M9 AP.

Everything works fine except WhatsApp video/call

Model                      : Deco M9 
Hardware Version   : V1
Firmware Version    : 1.4.3 Build 20200918 Rel. 75286
ISP                          : Ziggo
Configuration          : Access Points
Network diagram    : Modem (Ziggo) --> Router (ASUS RT-AC87U) --> 1. AP (Deco M9) no problems 
                                                                                                            --> 2. AP (Deco M9) can't Whatsapp video/call 

Connection              : Wired (to router)

Fastroaming            : On/Off makes no difference
Beamforming          : On/Off makes no difference
Tested on                : Samsung S9, Samsung A5, Motorola E6

I have changed the AP to router mode and reset the device many times, also reinstall the latest firmware but without solving the problem.
both AP have the same firmware and configuration, but only one AP gives the problem.

@Elgato77 

Still no solution as far as I'm aware. 

Shocking considering the cost and all of the glowing reviews. 

I'm disappointed in the solution, but haven't had the time to pursue any deeper... 

In my case I frequently (constantly after I don't know - 10 mins) that "whatsapp is using mobile data". 

Hard to say if issues are masked on laptop etc, if perhaps a brief drop out, but I get it sitting within 1 metre of the deco, and not moving anywhere in the room, let alone moving closer to a different deco. 

Something strange going on. 

Samsung s9+ phone. 

@RMarquez 

Thank you for your reply, unfortunately I am on the latest version

@MarkN @TP-Link_Deco  Same problem whatsapp calls and video dont work. Deco M5, latest firmware. irritating.

@MarkN 

I am also having the same issue and when I researched a lot on net I have found out about this GBWhatsApp and after using it my problem got solved.