0% retention after 35 signups. Advice?

Been building Culink (a link-curation platform) for about 25 days now.

So far:

• 639 visitors

• 35 signups

• retention close to zero

From what I can tell, it doesn't feel like a product problem — users who try it say it makes sense — but I can’t get people to come back. So I’m guessing this is more of a GTM problem.

Tried:

• Reddit → links removed or auto-filtered

• Paid ads → no traction

• Product Hunt → barely moved the needle

At this point SEO feels like the only remaining channel, but that’s a 2–3 month wait at minimum.

For those who’ve been in this stage before:

How did you get your first returning users?

What channel actually worked for you?

Really appreciate any insight — building solo can feel like guessing in the dark.