First, I think you need to look at why no one showed up for your writing on Medium. Did you just publish and forget it? What's your view-to-read ratio? Are the people reading your articles engaging with it (or at least reading to the end)?

Selling ebooks is about 5% writing and 95% marketing. I wish that weren't the case, but the fact is that most ebooks are utter trash: riddled with typos, mostly packed with useless information, and generally executed poorly all around.

But those terrible ebooks sell because they're marketed well.

You can find tons of free resources on marketing, or you can buy (warily) any number of books about marketing ebooks online. You can also talk to someone who's helped other people set up successful ebook-selling operations — I'd be happy to help.

The basics are:

1. Write something people need. If no one has the problem you're solving, it won't sell.
2. Put out lots of content around the subject matter on your own site/Medium that links back to your sales page for more info/next steps.
3. Write for other sites with big audiences. Guest post about your subject matter. Most sites are constantly hard up for content, so you have a decent shot of getting a post run of you submit it properly.
4. Be consistent. You can't run two guest posts and expect millions of dollars in sales. Many of the best sellers are putting out dozens of articles a month.
5. Test and iterate. Set up simple split testing on your site. Watch the conversion rates from your articles and see where spikes and dips are happening. Adjust as necessary.

Making money from ebooks is not easy, and it's mostly an effort in self-promotion and sales. But if you follow through and keep testing, there's a lot of money to be made.

If you'd like an experienced set of eyes to help with putting together a launch/marketing strategy, I'd be happy to give you a hand. Let me know.

Good luck!