12C display not working

[Brianr88117]

Hello,

I am new to the forum and a complete beginner. I own a 12C which I purchased back in 2014. I used it for about a year then it went into my top drawer in its leather case, not to be used until recently. When I turned it on, the display hardly showed any numbers, but it was attempting to show me some. I changed the batteries to ones from a pack that I had in a drawer, but that yielded the same results.
Upon a serial number check this calculator was made in China in 2012, which doesn't seem that old compared to what I'm reading about the history of this calculator.
I tired the reset button located near the battery compartment, no change. I tried the (-) sign reset no change. I tried the paper clip to connect the + and -, and drain the capacitor, no channge. Before I purchase another 12C, I was hoping there was a way to fix this.
I did read that someone warmed up the screen connections from the inside, but I have no idea on how to open this up properly.
Any help would be appreciated.