I recently added another site admin to my Backrop site. The Admin bar works great for me but does not appear for him.
I did see this possibly-related post and tried the suggestions there. None worked for us.
https://forum.backdropcms.org/forum/admin-menu-disappeared-after-updating-core-1293
Currently using latest Backdrop 1.31.0 but had this problem with 1.30.2 before updating as well.
Any thoughts?
Does the Administrator role of your site have the permission "Access administration bar"? (I think, you wouldn't notice the missing permission if your own account is the so called User 1.)