I have an issue where I have a dataobjectmanager installed and working well on my computer and several others.
However, the client has just rung to say that she cannot see any of the "Add [Dataobject name" buttons on the CMS. She has provided a screenshot and I can confirm that there is just a blank white area where the button should be.
Yes she has flash installed. And I have had her clear her cache in Firefox.
The only condition on that display is the "Add" permission. Make sure you haven't removed it. It should be on by default. If you can, check the markup and make sure it's being drawn. If it's not, it's definitely a permission issue.
Well, you can set $dom_field->setPermissions(array('add','edit','delete')); for instance. By default, all the perms are on. One thing to check would be to pull the <% if can(add) %> checkpoint out of DataObjectManager.ss and see if it makes a difference.
If it does, you need to use setPermissions() to get that condition to pass.
Also, make sure the markup is not being drawn. it could be that the markup is on the page but a CSS bug is causing it not to display.