I noticed that after working on a file for a while, the bounding box doesn't highlight the shapes I hover/mouseover. on other files, it does highlight the shapes I hover over. I know about the command+shift+b and the command+h, but it doesn't solve the problem.
Sorry to hear about this. In addition to correct responses given by Charu, please check out this help article to know how bounding box works and this help article to know how you can lock or hide or unlock the layers/objects.