Hello @Luinenburg,
Thanks for writing in!
First, please go to Settings > Permalinks and change the Permalink Structure to any of the choices excerpt using plain.
2nd, you may also check out Cornerstone > Settings > Permissions and make sure that the editing if the pages, posts and other settings were enabled.
If nothing is helping, please provide us access to your site so we can investigate the issue further. You can create a secure note in your next reply with the following info:
– Link to your site
– WP login URL
– WP username
– WP password
– WP Administrator Role
– Confirmation that we can access and make changes to your site
To know how to create a secure note, please check this out: How The Forum Works
Best Regards.