They ignore you!
Recently, my algo placed a trade in the middle of the night and IBKR decided to block the trade and insisted on secondary mobile phone authentication. The trade was not outsized compared to normal, I've traded this ticker before, I had enough equity and margin available. I've haven't had this authentication in the last five years or since this instance. I was never notified of a new authentication method for trades. The lost trade cost me around $3,300. I've submitted two formal complaints about blocking and/or faulty trades with evidence and all I got was this response - 'We see that the mentioned restriction is removed at present. Hence, we are closing this ticket from our end.' I've gone as far as calling them directly and I've been told they only deal with commercial customers directly. THEY DON@T GIVE A S%^T ABOUT ME/YOU! If you're fine with that, good luck.