How do I fix my dough after I did not activate the yeast properly?
Putting it in the fridge probably didn't help matters any. If you had left it on the counter overnight it would probably have gotten its act in gear without further help. Yeast works slower when cool than when warm, but it does work, given time.

IMPE, dry packet yeast going bad is somewhere between rare and unheard of - unless it's stored somewhere that is too hot, or the "warm liquid" is over 115F, and that's not going bad, that's killing the yeast. Stored in the fridge, it lives effectively forever, certainly years past the expiration date.

If you have some yeast left, or buy a new packet, rehydrate it in a little water (a tablespoon/15ml or so is plenty) at about 100 degrees F (38C), give it 5-15 minutes of undisturbed soaking time, and mix into the dough - add a little flour if needed to compensate for the additional liquid.