End-to-end-encryption app is not visible

I have a managed Nextcloud server at IONOS and i want to test the E2E encrytion. I followed the instructions here: https://www.techrepublic.com/article/how-to-enable-end-to-end-encryption-for-the-nextcloud-app/

But i come to a halt at the point where i should activate the E2E encryption app, it is simply not visible!?
Unbenannt

Any ideas how to solve this problem?

Thank you in advance!

BR
Bertl