re: "If I hire someone and they do not fix my issue, do I still have to pay?"
As a general rule, if you hire anybody on Upwork, then you should expect to pay them.
To answer your question more specifically:
If you hire a freelancer using an hourly contract, then you pay them for their time, whether or not they fix your issue.
If you hire a freelancer using a fixed-price contract, then you are hiring the freelancer to provide a specific deliverable, or accomplish a specific task. If the freelancer does that, then of course you should pay the agreed amount.
If the freelancer does not "fix your issue", then you still may need to pay. But you may be able to get a refund. You can REQUEST a refund. But the money IS PLACED IN ESCROW and the system expects the money to be released to the freelancer.
So you can click a button to request a refund, but if the freelancer does not agree, a dispute would be triggered.
Every honorable freelancer WILL grant you a refund if you hire them with a fixed-price contract to do "Task A", and they completely fail to accomplish "Task A."
So that seems pretty simple right?
It means you get your money back, right?
What if the freelancer is NOT honorable?
Upwork's Escrow-processing server has no way to "look" at your server and determine whether or not "Task A" was ACTUALLY accomplished.
And what if "Task A" was accomplished 90%, but you want it to be accomplished 100%, and you ask for ALL of your money back? And the freelancer refuses?
You can see how things CAN get complicated.
Usually, though, this is fine. I have hired over 100 freelancers on Upwork and usually things went great. I think it is a GREAT tool for clients to use to get work done. BUT: I am aware that the percentage of successful contracts is NOT 100%.
If the job is not completed to your specification, then you should not pay. Okay, so the money is in Escrow but it cannot be released until you approve completion.
After waiting past the deadline and getting no completed solution, it is worth nothing to you so why pay? It doesn't happen often but I do get stuck with freelancers who cannot complete the task, and sometimes have been asked to release half payment because they realise that they cannot complete it. They should not have applied in the beginning and by now your schedule is blown.
So simply cancel the job while reporting whatever their failing was, and seek full refund unless you have received anything of value which can justify part refund.