My guide to know if your startup is failing:
My Qualifications: Every startup I've joined has failed. Not necessarily because of me.
For the sake of me typing faster, x=startup.

1) X doesn't have a product, but just an idea that x keeps pitching as the next "big thing". (What's with this shit anyway?)

2)X keeps changing products, One day your designing IoT sex toys and the next day your building a self aware AI. For some reason, the people at X saw Silicon Valley or that meme about how Instagram was created and thought "Fuck that happens to every moron who can switch on a computer."

3) Even worse, X keeps changing industries.

4) X keeps lying to you, your marginal user base and seems overall unethical. (You should leave at this point.)

5) X wants to target some obscure and very specific market and keeps pitching the company along the following lines
<famous_company> for <random_market>
Eg: "Yo bro it's like Amazon but for necrophiles."

6)X keeps saying that X is the next big thing. (X is not and I can't emphasize this point enough.)

What you should realize is this is my general observation and some or all of these points may not apply to every situation.

Sorry for typos and any other stuff.