Pattern Sr Software Engineer interview questions

I had an internal referral and a phone call with a recruiter. She did the usual resume review and explained the position. She was basically saying the first couple were formalities since I had a referral. She left saying she'd get back to me after the weekend. I never heard from them again. I reached out multiple times only to be ignored every time. Was not impressed, especially since I had a referral. You can't even tell me what happened?

Process is straight forward. They took 3 tech rounds (1 was screening and 2 was 1-1 interview on zoom). I cleared all of them. I am really disappointed by their final round which they call it as top grading round. They rejected me in this round without providing any strong feedback and simply ghosted me. Later I got to know from my referral that I have been rejected. They didn't even took efforts to provide me feedback despite of multiple follow up.