Tribes can have a maximum of one blog assigned to them at a time.
To prevent members from switching between multiple blogs, you can only edit blog assignments for a tribe once a month. In other words, if you assigned Blog A to a tribe today, you would need to wait 30 days until you can assign Blog B to that tribe.
If you've accidentally assigned the wrong blog to a tribe, and you cannot change it, contact us. Just let us know what the proper blog assignments should be, and we'll make the change for you.