Today, I caught up with my good brother who is also an entrepreneur and found out that their Agent product has been in a pilot for half a year for a certain leading cloud computing platform in the country. The other party hasn't paid a single cent and is still working on it, which made me so angry that I almost wanted to scold him on the spot.

Convince one if you can, let business return to business. The ones who give you money are customers, and those who don't are just noise. You need to endure the hardships of customers and train your company's and product's ability to make money. Don't suffer from the noise, as it will cause you to lose focus - a non-paying customer won't care what you do, and following them will lead you astray.
Finally, a complaint: domestic big companies just love to take advantage of customers. Even if they work hard for half a year and provide good service, the probability is high that the other party will not make a purchase but will immediately replicate it internally after validating the demand and technical feasibility. Moreover, when it comes to overseas financing, the endorsement capability of any domestic big enterprise logo is not that strong.