Ask HN: Unsuccessful one-person online businesses?

On the flip side of yesterday's "Ask HN: Successful one-person online businesses?"

> How many people on Hacker News have run an unsuccessful online business on their own? What was your business and what was your analysis as to why it was ultimately unsuccessful?

> Were you able to apply the lessons learned to achieve success at a new one-person online business?

[0] https://news.ycombinator.com/item?id=21332072 (Shout-out to user trikko, whose comment on yesterday's Ask HN inspired this post.)