I saw that the question Why can't I see some of the job postings of some members of my Upwork team? is untagged. I'm guessing it used to have the upwork tag but I could be wrong. Was the tag "Upwork" removed, and if so, why?
Tags having only one question that either haven't tag excerpt / wiki are automatically removed. This is a standard feature of SE and already discussed in Meta SE -> What causes a question to be tagged as [untagged]?
Users having enough rep can add the tag again. It might be worthy that tag wiki be added to prevent the tag to be automatically removed again.