If there is too much moisture, the seeds may become moldy instead of germinating. And if there is too little moisture, the seeds will remain dry and will not germinate at all.
You can also try 4 tablespoons instead of 2. I used 2 for greater visibility and the likelihood of spoilage is lower in smaller amounts because like that it has better airflow.
The jar should not be exposed to direct sunlight. The jar is exposed to direct light only for the purposes of the video.