"AnatomicalStructure" is an Interpreter type and I imagine that that might have issues under a slow internet connection. However the issue with TravelDirections and so on above is a bug rather than an issue with connection speed. I have been informed by the developers that the issue is resolved and will be fixed in version 10.4 or perhaps via a paclet update. I am not sure that I understand the circumstances where certain issues can be pushed via a paclet update. So, for the time being assume that TravelDirections, TravelDistance, and TravelTime are broken.

the 10.3.1 update! It worked fine in 10.3.0 (the version I used for this post). OR it could be a problem on Wolfram's side of course. I already deleted 10.3.0 so I can't test that one. (Mac OSX btw).

Interesting that there will be a 10.4, not an 11 ;-) They always did .1 or .2 updates, so I was already surprised with the .3 update! Well, maybe this is a new kind of updating!

This is not (I believe) a calculation that involves alpha calls: TravelDirections is a part of the Wolfram Language itself, though it requires cloud access to function.

However, I notice that the first example in the Documentation Center for TravelDirections,

TravelDirections[{Entity[ "City", {"Miami", "Florida", "UnitedStates"}], 
  Entity["City", {"NewYork", "NewYork", "UnitedStates"}]}]

also fails with $Failed["ComputationTimeout"] so something must be amiss with the server.

Something for the developers to attend to, I think!

I suspect that TravelDirections is simply broken at the current time.

Note my comments earlier. I have discussed the issue with the developers, they are aware of it, and the problem will be fixed in a next release (whatever it is officially named).

Thanks to everyone for the replies. Three days later I just tried again, without any luck. If it's a Wolfram-side issue then it's a persistent one. I haven't done the 10.3.1 update yet, by the way.I'll do it today and see what happens.

UPDATE: 10.3.1 now installed and the problem persists.

In addition: it's strange because the 10.3.1 update specifically fixed some bugs with TravelDirections...

I am experiencing that problem quite regularly, e.g. in the context of AnatomicalStructure. My interpretation is that this timeout were due to my slow internet connection. I then have to try several times before I eventually get all the data. It would be interesting to know if this is the real reason.