DeX mode not starting after Android security update After recent two Android security updates, Samsung Galaxy Note 8 plugged into a DeX station is unable to detect it and therefore it is not offering the notification which allows to turn on the external monitor or going to DeX options.

Attached keyboard and mouse via USB ports on Dex Station still work fine with the phone as it is. Only the DeX mode recognition seems to be gone.

What I did try:


An advice to plug the phone into DeX Station unplugged from the power and the re-attached the power cable but it did not help the DeX recognition.
A troubleshooter from Samsung. Update was completed, no change.
Trying the device elsewhere with a Galaxy S9 phone. It worked normally.
It was an HDMI connectivity issue.
If there is a connectivity issue to an external monitor, for example HDMI cable is detached or damaged, the DeX Station behaves exactly as described above. Everything in DeX Station seems to be working except of the external monitor which remains blank and also there is no DeX item among notifications.
My assumption that the external monitor will start working after the DeX notification is clicked was wrong. The monitor should always produce the image from the phone when the phone is on. Only then the DEX notification follows on the phone.