You can thank IB for the data problems. They have a long history of data outages. If you trade major money you have no excuse for not having a backup data provider. ........ REDUNDANCY
Ok, I just called the Helpdesk in Switzerland. The problem is known to IB, they are working to solve it, but there is no estimate of time when it will be solved (my guess: after the US-Boys have started to work).
They recommend to restart and re-login to the TWS: then the data should download.