Did you talk to your existing investors? They should have a useful perspective on your options.

They invested 5 years ago. That means by the time you run out of cash, they're 6 years in. Most VC funds have a 7 year life, so unless you got cash very early in the fund, they're likely at the point of needing an exit. Given your description, I suspect they've decided your company isn't going to make it.

Can you have a frank conversation with them about this?

If they still believe in the premise, despite their first $4m being effectively written off, that will alter your strategy. If they believe in the team, but not the current product, that's a different strategy. If they're done, then you have a third set of options. You need to know which way they're leaning. Of course, they'll always try to leave their options open, but an honest assessment from them is very valuable.

Then you need to think about your team. If one of the founders is working full-time at another startup ... I think you've got a problem. They've basically quit without quitting, and the company is letting them coast along because you're all friends.

You should resolve this situation: either they're in or they're out. There doesn't need to be any shame or ill-feeling, but it's not reasonable to have someone giving a startup anything less that 110% of their focus.

The fact that the other two founders are also "super casual" also raises an alarm. Why? Do they a) not care anymore? b) not see a problem? c) believe in a solution you don't? What's going on? The company leadership needs to be united and focused.

You will likely need to strip expenses to extend your runway as far a possible, especially given that raising funds now is likely to be slow. This might mean you need to cut the team some. You should also think about whether the founders' salaries should shrink too. Do a general tidy up of stuff: cull unnecessary subscriptions, audit your cloud bills, etc, etc. This is a critical time.

Finally, but perhaps most importantly, it sounds like your product is in trouble. You're not committed to it: you've pivoted once, you're flirting with an IoT play, maybe you can sell your data ... this all sounds like you don't have a clear vision nor a commitment to it. I guess it's not news to you that this is not a great time in your company's life to be having these doubts.

You said "users don't stay on the platform". That seems like something you very much need to understand. 500 people is a useful sample: why don't they stay? Is there something they don't like? Or does it just not provide (enough) value? What does it need to do to fulfill their needs? You should be very focused on figuring this out and fixing it.

It's always possible to raise money. People with money, especially in a high-inflation environment, need to put it somewhere where it's earning a return. That's not to say that aversion to risk doesn't go up and down, but ultimately they're losing money if it's not invested somewhere with decent returns. If you've got a passionate, strong, united team and a product that's got traction and fit, you've got the best chance of getting that next round. Your next quarter should be spent getting those pre-conditions sorted, and then you've got 9 months to close the deal.