Critique my side project -- high usage but bad conversion

So I recently launched a Gmail add-on that makes it super easy for folks to share any email thread within their company. The basic concept is that the software formats the thread to make it beautiful and easy to read, and then gives you a unique URL that you can paste into Slack, Gchat, etc.

The handful of people who have it installed are actually using it like crazy, so I think there might be some potential. At the same time very few people have it installed, and the conversion rate is very low.

Because it's a side project and there isn't any direct business model (other than eventually pointing users toward my startup, which is built on the same tech but has some more advanced features), I haven't put much time into promoting it and I'm not inclined to run paid ads. But I see that Slack has their own Gmail add-on that does basically the same thing, but much much less well, and theirs has 500k installs whereas mine has less than 100. So I do think there is some potential, but I'm trying to figure out if there is a way to increase the conversion rate and also a reasonably scaleable channel for promoting it.

The website is https://www.prettyfwd.com.

Any thoughts?

Alex