Unable to restart synchro!


I’m using Owncloud client (2.1.1+dfsg-1ubuntu1.1.) on my Ubuntu 16.04 laptop to synchronise folders between my Nextcloud server and my linux laptop.
I made synchronisations without problem till now. Then I lost Internet connection temporarily on laptop and when it came back I have never been able to put back the client in online mode !!! If I click on Account -> Connect (english translation of french text in app) it states me “Network access deactivated” unless Internet is fully working on my laptop without proxy or specific configuration !
How to get it back online and synchronise ?