Dear Sean,
thank you for your help. I am aware that they should be the same but the format without the yellow boxes does not evaluate - sorry I should have made that clearer. It is like in this post. If you ask for, say the population size, you do get an unevaluated function. In the "good" system you get the population size.
I cannot really pin the problem down. Mathematica works as expected on my 15+ computers. But it appears that on all the ones of a colleague it has issues. We are working with academic licenses. Some days ago we bought a Standard (commercial) license each for my colleague and myself. It is installed on a Windows server, where I first noticed the problem. When we checked my colleague's computers (>5 independent machines), they all had problems. Also one of hist Post-docs seems to have the exact same problem. First we thought that it might be because they run a more recent version of Java, but that does not explain it. (Downgrading Java and new install does not fix it.)
Also I have noticed that there could be a server issue at least contributing to the problem. I don't think that this explains it all. Here is what I see on one of the one for the problematic system:

And then the one for the ok system:

This is curious because both computers are connected to the internet. They are in the same network and have the same network config as far as I can see. I have not had the time to test this systematically though. BTW, I would to ask for the population of Berlin like that with an "=" sign at the beginning, but if I do it in the standard way with EntityValue, I do just get the input unevaluated.
Anyway, on the good system, the "plain text command" and the orange box one seem to evaluate fine. On the other system they do not.
Oh, yes, on all systems, when I use the Preferences tab to check the internet connectivity, all systems say that they can connect to the Wolfram server.
Best wishes and thanks again for your help,
Marco