Found the culprit, thanks to Marty!
I have been in hospital the last weeks and will be for some time.
Here I have access to an unencrypted public network (hotspot) only.
It turned out that that is blocking the access to the database, without warning that it's blocking this.
Luckily I can also use my mobile as a router.
That solved the problem.
So Schiphol is there for me too now.