Guidance on Startup MVP idea validation - I will not promote

I'm a solo dev. I built a reminder app because I forget things constantly, and every reminder app I tried lived on one device and felt like a chore. It's called RemindMe. I know the name is generic. That ship has sailed. You type "remind me to turn the tap off in 10 minutes" in plain English, and it fires on whatever you're near: PC, iPhone, or Android. It's a PWA you install, so no app store. If you don't mark it done, it nudges you again on a schedule you choose, with a hard cap so it can't turn into a notification flood. Then I built a second thing on the same engine, aimed at businesses. You import your client list, send them a question, and each one gets an email with confirm, decline, and not sure buttons. Every answer gets written into a log you can export. The selling point isn't the reminding; it's having a record of who replied and when, for the moment a client says "I never got that." Now the part I'm less happy about: 4 real users. All stopped using it before I'd improved anything, and none came back. I asked all of them why, but got no response. And I have not spoken to a single business owner about the business version. I built it because I could. So I'm not asking "is my idea good?" I'm asking people who've been further than me: When you had 4 users and no signal, what was your literal next action? Not "do marketing." The actual first thing you did on Monday. How do you find 10 people to talk to in a niche you're not part of? I'm a developer, not someone who spends their week chasing clients for confirmations, so I have no network there and cold DMs feel like spam. Would you kill the consumer half? I can't beat Google and Apple at free reminders. But it's the half that works and the half I use every day.