Can't make a cell absolute when referenced to another worksheet?

Hi. I'm been searching for an answer to this problem for days, can someone please help me out. I would greatly appreciate it!

To keep it simple, this is what I'm basically trying to accomplish. I have two sheets, say Sheet1 and Sheet2.

On Sheet1 I have an IF statement. =IF(Sheet2!C5="OK","OK","-"). This works well, however, when I put a new row in Sheet2, it adjusts the C5 formula in my Sheet1 formula to C6.

I want the formula in Sheet1 to always stay referenced to cell C5 on Sheet2.

So I learned that I can use $ to make absolute references. But for some strange reason, Sheet2!$C$5 / Sheet2!C$5 / Sheet2!$C5 are all failing to accomplish this.

I don't understand what I'm doing wrong. Can someone please help me out. Thanks!