sidebar not appearing on mobile

sorry it was my mistake my custom css was the problem

Are you sure it disappears ? It slides to the bottom of the content in extra small screens but it should not “disappear”.
I’ve never encountered or recieved such a bug. You can view or play with the demo here: https://eodepo.com/wp/demo/bootstrap-ul/responsive-layouts/

I could have a look to see what the problem is, if you have an online link.

OK, saw your 2nd message after posting, glad you got it sorted out. Marking as resolved.