The coding of the sub works fine (at least here on Excel 2003) however
there are some points to mention about both formulae on the worksheet:

1.Your formula: {=SUMIFA2:A8,"="&C12,B2:B8)}
You've got curly brackets around it, I'm guessing you typed these into
the message yourself, manually, rather than copied them, as it's what
you can see in the formula bar. This means you've array entered it
(held down the Ctrl and Alt keys while pressing Enter), which in this
case is not necessary. Committing the formula with just Enter is fine.

2. Your formulae are both missing an open parentheses directly after
the F of SumIf.

3. The part of your formula:
"="&C12
doesn't need to be so complicated, just
C12
will do. So your final formula can be:
=SUMIF(A2:A8,C12,B2:B8)

The same applies to both formulae.