Hello Matias Baumann , and a warm welcome to our Forum!
I am sorry to hear you're experiencing this issue at the moment, would you kindly let me know if it helps to access the Material Editor via the context menu instead:
If that makes no difference, could you also let me know what exactly the problem is? I reckon you are clicking on it and there's simply no further window/dialogue opening what so ever?
Should that be the case you can also try to fully re-install Enscape once (uninstall any existing version and use our latest installer afterward), and if that also doesn't help we'll need a dedicated feedback report (including logs) submitted by you as detailed here.
Thank you very much in advance for your cooperation!
Hello Demian Gutberlet, sorry for not replying sooner.
I was on a tight deadline to deliver some renders.
I reinstalled the new version and now it seems to be working fine.
Thanks for your attention!