Why can not I vote to reopen the following question? (No button available)
On structure of certain universal $C^*$ algebras (An attempt to Non Commutative (Torus) Knot theory)
Why can not I vote to reopen the following question? (No button available)
On structure of certain universal $C^*$ algebras (An attempt to Non Commutative (Torus) Knot theory)
As already mentioned in the comments, only users with at least 3000 reputation points can vote to close and reopen. See, for example:
It is worth pointing out that even users below 3000 reputation point can ask to reopen a question - one possibility to do so is on meta. There is also a thread intended for this purpose: Requests for reopen and undelete votes for closed and deleted questions. (I interpreted your question as a question why the reopen button is not available - as opposed to a reopen-requestion for this specific question. So I have answered the question in this way.)
Also, if you edit a question and check the checkbox "This edit resolves the original close reason", then the edit puts the question into the reopen votes review queue - where other users see your question and they can vote to reopen (or to leave closed).