Menus have disappeared on my Oxygen theme website

My primary and Secondary menu have disappeared from my new wordpress site. I am using the Oxygen theme.

I am new to this and have trawled through the previous forum posts on the subject but nothing has worked so far.

I have not installed or activated any additional plugins so I don’t think this could be the problem. I am not programmer literate either and have no idea how to write code so I wondered if there is some other form of trouble shooting I can carry out in order to ensure the menus are visible on the home page.

I have set up each menu which appeared last night but now only the subsidiary menu in the footer seems to appear on my site.

Can anyone help?

Thanks