Figuring out the Principal Remaining on a Loan

But PPMT will show you only what part of loan principal have been paid during given period
and of course it is increasing every period, as your remaining priincipal decreases, every next period you pay less interest and more principal.

If your aim is to see remaining principal and you want to use PPMT, then leave formula in B4 as is
But in B5 (and copy down) write a bit different one:

Formula:

=B4+PPMT($E$2,1,$C$2*$D$2-A4,B4)

PS. I'm by no means expert in financial functions (nor in terminology, especially in English), but probably "most appropriate" function here would be CUMPRINC - like (B4 and copy down):

Formula:

=$A$2+CUMPRINC($E$2,$C$2*$D$2,$A$2,1,A4,0)