Can i be in trouble for my company's system error?

Ok, I have FMLA on my job had it about 3 years now for my medical condition, so at my job we can either call our FMLA time in or put our FMLA time in on the computer, so I do that with no problems, checked my hours since there on rolling 12 months, no problems all shows great, so low and behold one day my boss pulls me in a conference room hands me this paper I need to sign and says its my written warning!!! I'm at this moment shocked,confused, and very upset. Told her I didn't agree with this because I had the FMLA time it was put in and I got no response saying it was denied... So my boss asked if I had looked at it recently I said no not since I used my last FMLA date, and my company they send you letters if they are approved or not and they send my boss notice and if you get down to having used all of your time you get a phone call and letters to... So I didn't not know there was any issues with my claim because I got no denial letter or call... So after my boss puts me on my written I go and check my FMLA and what do I see I have tons of days that were approved, that were put in approved, that then showed now as pending... So here I am in a frantic wanting to know what is wrong, so I email my FMLA unit and get no response, I get a phone call a few days later saying my claim is under review for over review, basically that means I was putting in my FMLA time like I always do, my work approved it, and then out of the blue my work who never told me what was going on said, yes my days were going through with no problems they days were approved, and then after someone looked at it they said oh the system is not updating my FMLA hours, and then my job went back and the days that were approved are now denied as Exhausted.... My boss said it is my responsibility to keep an eye and make sure there was no issues, and I did just that I put my time in like I was supposed to, looked hours showed just fine.... But yet I cannot go update my Job's software!!!! Or can I update the year to date stuff that is what the FMLA unit does... So now I got this written for me doing the right thing, is it ok for my job to do this and turn it on me and get me in trouble? I do not see where I did not do my part correctly, because I put my time in and they approved it, then turn around and deny them and penalize me for it when I never got letters or calls saying I reached xxx amount of time used because of my Job's system not updating my hours... I don't see where this is my fault at all. I want to go to my HR department but I am kinda afraid to because I don't want retaliated against and worse lose my job!!! I really do not know what to do any advice would help me decide if I am going to my HR or to the DOL, am I really the one who should be in trouble here??? Thank you for your time, I live in Ohio