Ask HN: Your SaaS that didn't take off

I have been working on an app for 2+ years now (not continuously), planning to do the Show HN this year and eventually, possibly, turn it into a SaaS.

I am very new to this sort of thing and don't expect too much from it. Whilst thinking about it I was curious: What are some SaaS that were tried out, looked good on paper, were actually launched - but somehow never took off?

The goal here is to try and take away some lessons as to what caused those SaaS to "fail", that a new launcher like myself could take heed.