Thanks a lot for your advice of going via avios.com. That is indeed a good option which I did not have in mind.

Unfortunately my IB Plus account is not yet 90 days old and I cannot get it activated as all fails.

Do you know if there are currently any quick possibilities to activate an IB Plus account that is not yet 90 days old?

My new IB account has 9-digits (I learnt earlier it was 8-digits). I tried tried to register for Erewards but failed, as my IB Plus number could not be recognized.

Amex rewards says transfers to IB's new 9-digit account do not work and Marriott Bonvoy transfer failed as well (error message: "number cannot be recognised").

Buying Avios is currently also not working at IB.

Very frustrating as I urgently need to book an Iberia reward which is not available at ba.com, but still shows 2 seats at iberia.com. I need only 1150 Avios to book it and would like move them over from BA.