Root Beer carbonated but not fizzy

Hi, all. I've made 4 batches of root beer in the last few weeks and had a similar problem with 3 of them - the bottles firm up nicely, but the soda doesn't feel carbonated.

I've left them on the counter until the bottles feel as firm as a commercially produced soda, tasted, and let them sit on the counter until they feel even firmer. I think the second batch was the one that carbonated as expected, although the first batch carbonated when I let it sit until I was scared about explosions - probably a day and a half after it was as firm as a commercial bottle.

Same method with all 4 batches: mix ingredients by shaking, pour into 3 20oz bottles, let sit.

Batch 1:
1 T. gnome extract
1 c. sugar
1/4 t. baking yeast

Batch 2:
1 T. gnome
1/2 c sugar
1/2 c honey
1/4 t champagne yeast

Batch 3:
1 T. gnome
1 c sugar
1/4 t. champagne yeast

Batch 4:
1 T. Rainbow birch beer extract
1 c sugar
1/4 t champagne yeast

once they firm up, chill them. CO2 is a lot more soluble in cold water than warm/room temp water. You're building up plenty of CO2 in the bottle headspace, but more will dissolve into the liquid when cooled. hopefully that'll fixya.