Thanks canne.
~I just didn’t see I had to enable the access key under the OAuth tab. (No clear idea what this is, if it is related, but it is working now.)~
edit: I believe I did enable both API key and OAuth. But only one enabled API key is necessary. Nothing to do under the OAuth tab.
edit: actually, only HERE maps were working but not the HERE routing.
Now, both are working. Details here.
Sorry for the mess…