DUI probation includes a relatively large amount of conditions, so congratulations for completing all but one of them.
The one condition you have not completed is significant, for you have only completed 1/3 of it. Due to that fact, you are now facing (1) jail time, (2) even more probation, or (3) termination of your probation, albeit "unsatisfactorily" with, likely, the uncompleted condition outstanding (you must still complete it).
What happens in your case depends on your criminal record, your attorney, the prosecutor, the judge, and your probation officer.
If your probation officer is correct in that the judge presiding over your case does not allow hours to be bought out, that is too bad, and I believe rare, especially in our times where city, county, and state government (not to mention our national government) is so far in debt.
DUI is arguably the most serious misdemeanor charge (and can be a felony charge after so many o fthem, etc.) in Florida. Do not expect anyone to take this matter lightly.
First, I would not accept the P.O.'s answer as being the "gospel" on that issue. An attorney can contact the judge directly and make a request or file a motion to either allow you to buy them out or to extend the time period, if that's possible.
There's always a chance. Unfortunately, no one can give you odds without knowing the judge and all the other players involved. Furthermore, even if one knows the judge, the judge is a human being, not a machine - thus, not as predictable.
Best bet is if you think you would regret not filing the motion, then file it. The least that would be done by any attorney would to argue on your behalf in court that all conditions except the CSHs have been completed, and that two-thirds of them have been done (better than one-thirds).
The more CSHs completed, the better shape you are in. Good luck.
You may be able to ask for an extension of the probation to complete the community service hours, if you have not done the maximum allowable time on probation.