Hi Alicia, that is brave of you to go again and try it out one more time. And I think you should never quit, just adapt and pivot slightly to make a fit for the audience. Now, I will be a bit more pragmatic with a comment and give you couple of hints for you to possibly make improvements in the future:

1. Conversion rates on courses generaly are around 1-2% depending on the platform where these are promoted or shared. Now, I'm telling you this just to consider the size of your audience and if it's big enough to actually see results eventually. I'm not sure about the format you offer though, but just be mindful...

2. Where are you promoting the course and do you invest in ads on any platform? Because I think you should if you organic audience size is too low. I mean, I don't advise anything since I really don't know anything about your budget or marketing experience... but if you have any spare time research this or try and find the courses...

3. Think about if speaking in public is the biggest problem your students have and if they perceive it that way. You know they have problem with public speaking, you see it of course, but do they know they have this problem? Do they need public speaking regularly and as part of their profession? Could you rephrase it differently, I mean the name of the course, and make it slightly more appealing for them?

I won't go any longer, and you might be doing just everything right here.. Don't mind my ignorance for suggesting because I'm just shooting what I see could be the issues.

Anyways, keep it up and I am sure you'll see the results eventually.