Can not connect with Tower 4.0 release

The 4.0 release was pushed to my phone and now I cannot connect. Radios connect (green light on solid) and red heartbeat blinks. When I press connect I see more traffic (red blinks more). I also tried various link speed and direct USB cable with no success. Phone is a Samsung galaxy S7 Active
I tried a tablet (an old Acer) which had Tower 3.2.1 and connection worked fine. Tower then updated on the tablet (it had been off previously) and now it has 4.0 and will not connect.
I removed 3DR services, but that did not help. I filed bug #1821 on this before I found the this forum, so I apologize for filing before asking in the forum.
Any other info needed?
What can I do to try and debug this?

Is conection set to usb?

yes. in both cases via 3dr radio and with direct usb cable it is set to usb and has the correct baud rate.

I have working in a Samsung J7 , If I can help comparing configuration let me know.
I have v4.0.0-beta9 and the cel have 6.01 android vers

I too am using android 6.01 and v4.0.0-beta 9. I occasionally see unable to access usb message even though I have set Tower as default.
I also see the screen blink like it use to with 3DR when I plug in the radio. I am wondering if there is some old driver still taking over the USB when I plug it in.

Solved: was due to sysid !=1 See new thread.

A post was split to a new topic: Problem with SysId != 1