Digits app: call tranfer & switch device don't work

Any body here using digits app installed on multiple devices and can not use either the call transfer or switch device options?  

I have digits installed on 3 devices.  I have a virtual line set up & active on all 3 devices.  All 3 devices ring with an incoming call. If device A answers the call and the call is for Device B . They would try to either initiate a "transfer call" : which allows you to chose a phone number to transfer call or "switch device" which shows list of devices that have the digits with the line setup. In either case the call is put on hold & either action freezes and the switch or transfer is never completed.  If you manually take the call off of hold ....while the call shows still connected with time of call still counting...the caller can no longer here me nor can I hear the caller.....so basically the call is lost /in limbo etc.

As anyone been able to get these features to work : transfer call to another # or switch device ? 

How did you fix issue & how to do contact digits support for help 

Gracias