Is this a fragment or a run-on?
Since I no longer maintain an office downtown for working on this kind of project.
That whole thing is a dependent clause. It is a sentence fragment.
If you omit "Since", the remaining words will be a complete sentence.
The given sentence is a fragment.
This sentence is a fragment, not a run-on.
A fragment is an incomplete sentence that does not express a complete thought. In this case, the sentence does not have a main clause and lacks a subject-verb relationship. It begins with the subordinating conjunction "since," suggesting that a dependent clause is following. However, the dependent clause alone cannot stand on its own as a complete sentence.
To fix this fragment, you could combine it with another sentence or add a main clause. For example, you could revise it as follows:
"Since I no longer maintain an office downtown for working on this kind of project, I have started working from home."