Bug offline

When I launch the Minecraft launcher it puts me playing offline and at the top left it puts me offline when I click on the button to search for the connection it always puts me the same even though my computer is well connected to wifi. I looked if it was not because of the Avast firewall but I did not activate it (since it is not free) give me a solution please because it is painful and in addition I love it Minecraft thank you. (I'm French so I'm not very good at English).