Does not turn on at all.

I have a Texas Instruments TI-81. It was in a cardboard box among other junk for some years. It has not been dropped, water-damaged or anything in all that time. I found it while my family was moving with no batteries in it except the watch battery. I got it some new batteries, but it won't turn on. In my robotics class at my new high school, I was able to remove the back cover and I discovered tat the cover was glued on using some sort of black gunk that I carefully cleaned out. Also, the components had been taped in place, even though there was no evidence that anyone had opened the back cover besides me. What now?