40 users but zero feedback, what should I do?

Try recruiting users via sales rather than marketing. In other words, find people out in the world, get their contact info, sell them (via conversation) on trying your product, then follow up afterwards. You can literally just go to a coffee shop, buy someone a coffee, and do this in person.

It's not the best method for getting large number of people in the door, but it is the best method for learning. And right now you haven't found product-market fit yet, so learning and building are more important than anything else. If you're not confident retention will be high, it's not yet time to try to recruit users en masse.

Maybe talk to them directly, or give something valuable (free) first and ask for feedback.

At this stage where you haven't found product market fit, it's best to talk to the users directly. Find where your users live online. Try to reach out to them individually.
There are 100s of ideas you can try from this curated list: first100users. I can't post the link here. So google it and you will get what you need.

If you can share the link or further details

What do you mean by not willing to give feedback? What did you try? How did you acquire those users?

If you know their email, send them a personalized, short message and ask them to consider giving you feedback. Make them feel special by letting them know that their input is important and appreciated. Don't overthink it!

I second what others have said here.

Find potential good pit users, get on a conversation with them (video call or in-person) and then give them access to your app.

From that point, since they already know you they won't just ghost your email when you ask "Feedback to improve"

Users drawn in from marketing just care less and so won't be as helpful.

I had this problem so I added a fixed "Feedback" button at the bottom of my web app. It pops up an input box and submissions go straight to my email.

I still have this problem..

Can you share some more details? Hard to answer without knowing what the product does or how the users started using it.

How did you get your first 40 users? And who is your target audience?

Do you have personal information like email or phone ?

Maybe you can try to contact them directly

What kind of business it is ?

Can you share the product name ? Maybe it can help determine the problem from our side ?

Craig, this is a fantastic resource. You’ve clearly put a lot of effort into compiling and presenting this information in a digestible format. The blend of science, psychology, and UX design principles makes this a comprehensive guide for anyone looking to enhance their landing page. I’m particularly impressed by how you’ve broken down complex concepts into actionable steps. I’ll definitely be applying some of these tips to my own website. Thanks for sharing!