In past years I would buy store bought basil plants. When they went to seed, they would drop their seed in the same pot

I grew them in & I'd get a volunteer come up in a few weeks. This season I'm trying to save the seeds & grow them in new containers, but none of them have germinated in the 3 weeks since I've planted them. The seed stalks were left on the plant until they turned brown. I then put them in a brown paper bag for 2 weeks before they were planted in 4" pots. The seeds came from Thai Basil & Red Rubin Basil. Any suggestions on getting these seeds to germinate?

John