MWI not working with Fritzbox

[frappy]

Hello,

I have a working answering machine on my Fritzbox Model: FRITZ!Box 7490 FRITZ!OS: 07.12

However, I cannot get my Yealink phones (T58, T42S, etc) to display a blinking LED and/or message on screen in case of new voice messages.

What I have already tried:

1) in Features > Notification popups: everything is set to Enabled

2) in Account > Advanced: I have:

- Subscribe for MWI: On
- MWU Subscription Period: 3000
- Subscribe MWI to Voice Mail: On
- Voice Mail: **600 or **601 or **602 etc depending on phone
- Voice Mail display: On

I can call the voicemail and listen to my messages, but I get no indicator.

What am I missing?

Thanks