Cellular data button greyed out, and no IP network

[AlainKnaff]

Yesterday I needed to use 3G, and noticed that it no longer works. The button to enable it in the Networking tab (obtained by scrolling from the top edge) is simply greyed out, and ifconfig shows that the IP interface for 3G is not up.

Other phone functions do work as expected (SMS, calls).

I use 3G rarely, but I did already use it successfully on this phone with this SIM a couple of weeks ago.

If I add another SIM (prepaid), 3G does show up for that SIM, and for my primary SIM it says "No SIM detected / Insert a SIM, then restart the device" (although I can still send SMSes and call using my primary SIM which is supposedly not present).

Suspecting some issue with my operator, I called them, and they told me that everything is ok on their side, and they didn't understand why it would not work.

root@alains-pocket-penguin:~# apt-cache policy ofono
ofono:
  Installed: 1.17.bzr6914+15.04.20160413.1-0ubuntu1
  Candidate: 1.17.bzr6914+15.04.20160413.1-0ubuntu1
  Version table:
 *** 1.17.bzr6914+15.04.20160413.1-0ubuntu1 0
       1001 http://ppa.launchpad.net/ci-train-ppa-service/stable-snapshot/ubuntu/ vivid/main armhf Packages
        100 /var/lib/dpkg/status
     1.12.bzr6892+15.04.20150407-0ubuntu1 0
        500 http://ports.ubuntu.com/ubuntu-ports/ vivid/universe armhf Packages