Over 10 hours passed and I have not received a reply from the author of this plugin (Site Offline or Coming Soon or Maintenance Mode). I have lost a day worth of customers and I worked all day to get my site back – thanks to external help. Not happy with this support.
I’ve managed to manually setup a new admin in the dbase, and now I can manage my site again.
Obviously, I have deleted this plugin that I do not recommend to anyone.