Custom Drupal (Block)Module not showing in Blocks
Code looks fine to me, except for the sometimes funky indenting :)

Your function lta_hoa_timeline() just returns ... in example code. If your actual code contains a whole of stuff instead of ... and you have trouble getting that to work/display, it might have something to do with the inclusion of CSS/JS files. At the very least you should see the title of the block appear.
But if ... is your actual returned content, it should work.

Verify that you've put your block in a region, that your theme displays that specific region, and that your block is not restricted to any specific page/role/.. , and you should see your block.
As suggested above, switch to a default theme, put block in a standard region like sidebar left, and turn off all restrictions