(parts of this message are from another post that Samsung deferred to non-US support without answering - using it because it exacly describes my problem) 2015 UN65JU6700F
It started showing an Updating tv software message (Updating tv software... Don't turn off the TV or disconnect the power cable until the update finishes) while I was watching an HDMI source. Once this message appears it never goes off and the remote and the controls behind the tv become unresponsive. The only way to get out this message is to power cycle the tv and continuously press the source button on the remote until TV is selected.
Once I go back to the source as tv, and a power restart will make the message disappear. However, if I select the HDMI source again, it will go back to the same problem.
I've tried troubleshooting using google but did not help except to get access to SVC menu.
1. I tried factory reset and rescanned channels - TV reception was fine on multiple antenna channels as long as source or smart TV buttons are not used.
2. I tried a SVC reset
In effect, none of my HDMI inputs or DLNA services are working.
I suggest calling into 1-800-SAMSUNG and ask for remote management for further assistance.