Trials usually offer full product functionality for a period of 30 days.
But sometimes, there can be several reasons why a trial may expire early: http://helpx.adobe.com/x-productkb/global/trial-software-expired-early.html
I understand, that you might not have done anything to cause this but soem other software system might have interfered with the trial causing it to expire.
I also don't think that there is any way to fix it.
What trial did you download? You could download and install one of the suite trials and try the products related to that for 30 days. It is likely though that whatever caused your trial to expire previously will happen again. The best option would be to try the software on another computer.