Removing item from Activities block

Question

I have an OG content type called "Task", and the OG activities block correctly shows a link to "Create Task". But I want that link to not appear and cannot figure out how to do it. I've tried using the og_links_alter hook which is firing, but not removing the link. I'm thinking that it might be one of two problems.

First, I may be using the wrong value in the hook's unset function (e.g. do I use "Create Task", or "create task", or "create_task", or "task", or something else).

Second, these links may be created by a view that does not appear in the normal views UI list, but rather is created by some code that I would need to change.

Any guidance on this would be appreciated. Thank you.