selecting object

malbe Toggle mask and Shape Path Visibility

if you'r not able to select object by clicking, are you able to selected via layer?

anyway also check if you layer was looked.

You need to be MUCH more specific about your problem.  In which window does this happen?  What kind of object?  Has this problem just started, or always been there?

AE allows you to select items in the preview window, but sometimes layers that are on top of that object can get in the way. Better to select the item in the timeline, in those cases.

But without better understanding your problem its not possible to offer good solutions.