This CERN Section/Hero issue is not limited to this website, I have encountered it on a couple of other new/fresh installations since November (see also this forum post). I’ve done done workarounds (ie. just stacked blocks), given I understand a centralised fix is coming. However with the refreshed WLCG site, the landing page module would be very useful to have…
How did you try to enable the landing page module in the first place?
Via the normal channel of …/extend and selecting CERN modules. Both all modules in one go, and when that failed, went one-by-one+save to find out where the blockage was. It’s Landing Page, Section and Hero header.
Here’s the clone site to use as a sandbox: https://wlcg-test-clone.web.cern.ch
Thanks! 
-cath