Bitdefender automatic update issue

Hello,

I have Bitdefender as my antivirus which was working very well until now. For a few days, it hasn't been updating automatically anymore!!! I have to do it manually every time I turn on my computer. Maybe I accidentally changed something I shouldn't have?

Can someone help me and explain in very simple language? I'm not very good with computers.

Thank you for the help you will provide me.