That’s odd; I was just able to test creating and GETting a tag by ID, and it worked fine for me. What comes back from the request when it appears to be successful?
Another thing I noticed when investigating is that object ID isn’t associated with anything in our database, tag or otherwise. Is that an ID you got back from Asana for a tag you tried to create?
One other thing worth noting is that you won’t see the tag in the UI until you tag a task with it, e.g. with addTag in the API using the ID of the newly created tag. This is for a number of reasons that are fairly internal to how tags are implemented, but it is something that causes some confusion.