You would have received a notification as to why you were "knocked back". Check your notifications. The only time it happened to me was when I tried to do a transfer but didn't have usd$25 in my account. If you're still not sure then why not contact IBKR?
The process I followed is below....
Click on:
"Transfer and Pay"
"Transfer Positions"
"Incoming"
select region as "United States"select the second option
"Transfer Shares Held at Transfer Agent"Input the details using your DRS Advice, add the number of shares, click complete etc
Did you follow the same process? I found it pretty straight-forward. The only other thing to check is that you have correctly set up your ID And tax residency status. You can check this under "Settings" "Profile information" "Edit"
