Ahah…it sounds 100% like me in September 2019. And i read about it so much before going in for the interview!!!
Like you, i got approved for an O1 (b) visa. My starting date was at the end of August 2019 so i kinda rushed after my lawyer told me i got approved to book the appointment. And i actually asked to accelerate the process _ get an interview a few days prior to what was proposed to me in the system_ which i should not have!!!
Because like you I GOT “DENIED” at the embassy because they could not find me in their system. At the first window, the man said “Oh, there seems to be a little issue, i can’t see your approval”, i said right away " is that PIMS?", he said yes. I asked if that was happening often and he also replied yes.
Then i did the formal interview with a woman. Everything was good YET she said she could not approved me that day because of pims and she denied me under 221g. She however kept my passport and said that i should get it back in 7 days with the stamp!
I emailed PIMS and even asked my lawyers if they send in a copy to KCC which they did.
Pims won’t reply as it has be internal.
For a week i was under ADMINISTRATIVE PROCESSING on the website of the government which by the way was down for a day or 2 adding even more panic.
I started to read tons of stuff online about people being in ADMINISTRATIVE PROCESSING for years.
BUT , exactly 1 week after my interview like the officer said I GOT MY VISA WITH THE STAMP!!!
Sadly now though, I and you WILL TO have to say YES, WE HAVE BEEN DENIED A VISA IN THE PAST on future application while it is clearly not our fault.
Ps- so far, i only used my visa for less than 6 months while i have it for already a year and half. Thanks to the travel ban European and this freaking pandemic