Update to Ubuntu 16.04 LTS Problem

Downloaded image worked fine. I have installed x-window and erpnext worked well also after that
But after automatic update of Ubuntu to 16.04 LTS ERP next is not working.
Just displaying “Sorry! We will be back soon.”

As I am beginner to Linux I did everything what I found but still when I do “bench restart” I get message:

http://localhost:9001 refused connection

Can anybody help? There was a lot of customisation already done in ERPNext therefore I want to avoid starting from fresh image again.

please share full traceback

Attached is output from bench start.
Problematic part looks to be:

Usage: bench [OPTIONS] COMMAND [ARGS]…
Error: No such command “worker”.