FGT60E Android Devices Zoom / Office365 problems

Hi everybody,

usually i try it myself as long as it solved but now i reached a point where i have no ideas, anymore.

Maybe someone of you can help me or have a idea what iam missing or doing wrong.

Here is my scenario:

- FortiGate 60E 6.2.3

- FortiGate 60E over VDSL 50 

- FortiGate has one Interface uplink with mutliple VLANs

Interface 1 (Network)

VLAN 100 DHCP active (Network 2)

VLAN 101 DHCP active (Network 3)

VLAN 102 (Network 4)

etc...

- FortiGate has one Interface uplink with an old network to supply the clients with the old Shares / DNS, which will be disabled soon

- to VLAN 100 two UniFi APs are Connected to provide W-Lan for clients

Everything works fine except two things:

Android Tablets with Office365 cannot sync E-Mails and the connection with zoom meetings.

What i have tried:

- Connect Windows Laptop over W-Lan to zoom = working

- Connect Windows Laptop over W-Lan to office365 = working

- Connect Windows Laptop over LAN to zoom = working

- Connect Windows Laptop over LAN to office365 = working

- Different Android Version Tablets connection Zoom over W-Lan = not working

- Same Tablets connection over LTE to Zoom = working

- Trying different Rulesets and ended with = VLAN 100 -> to any -> accept -> ALL -> no security -> no inspection Zoom / Office 365 still not working

- Updated Zoom APP = not working

- Controlled if UniFi APs have something enabled what they shouldnt have (like Packet-Inspection) -> nothing enabled

- Different other applications on the Tablets working normal and also playstore can update his apps

- Configured some FortiAP on a seperate Interface from the FortiGate to exclude Network Infrastructure issues or UniFi AP issues -> Connected Tablet to the AP -> Connected to zoom = not working

- Disable / remove MDM Software from Android Tablets and connecting Zoom over W-Lan = not working

We have different problems on the tablets

- One time audio worked, but no screen sharing and no video

- One time video worked, but no screen sharing and no audio

- Most time video not working, audio not working, screen sharing not working, but joining the meeting works

- Tablets get the information that screen sharing is active or video is active but black screen

- Same if i try to start video, screen sharing etc. on the tablets (the other getting information but nothing happens)

- Sometimes tablets do not even get to the point to join the meeting (connecting to meeting than hangs up - network issue)

- No E-Mail synchronisation with Office365

All Tablets are Samsung Galaxy

Summary:

Windows Laptops working normal in the same W-Lan

Tablets not working in the same W-Lan

And i already know, I´m just too stupid :)