No one signed up

I have a podcast for French women who struggle with learning English and I’m part of the online Coach Certification Programme. Now I’m more confident about my skills as a coach, I’ve offered my 88 subscribers 2 spots to test my free 6-week beta programme (I can’t charge for it before I have a business and that won’t be until September so I thought it would be good practise for free). I gave them a deadline. No one signed up.
I’m making it mean that I should learn how to offer that differently, maybe with a webinar. What do you think? What else could I be doing?
Thank you!