How to become a trusty external builder for submitting to flashbots relay?

Our team had ran the builder(from flashbots repo.) a long time, but only flashbots relay seems does not receive our blocks for validator (even bid is higher than other builders and even 200 ret-code return from API), so ,how to become a trusty external builder of flashbots relay, where can we get the pri/pub key to become a high-prio builder for submission?


We also have the same question. So far, we tried every channel to contact someone at FlashBots to understand how this works.
Can someone please explain what the missing step is?
We are a US-based builder.