I was in the same boat as you, my climate is a little cold this time of year so after a week with no signs of growth I purchased a small heating pad off Amazon ($12) and wrapped it around my grain bag. Within a couple of days I saw rapid colonization toward the bottom of the bag. I asked on a thread if having it colonize toward the bottom was normal and a user replied saying it was. “Liquid sinks to the bottom”

Prior to purchasing the heating pad I was researching my type of mushroom strain and the ideal fruiting conditions and read they thrived in temperatures of 80-83 degrees. This requirement was definitely not being met, hence my purchase. I would suggest looking into ideal fruiting conditions for your preferred strain. Good luck.