Hofmockel.org

symptom: Granted edit permissions to a user but they can not edit the node.

solution: If the user's role does not have the permission to use the
"input type" the node is submitted as, they will not be allowed to
edit. Check "admin/input formats" and make sure the role has permission
to submit with that input format.

ex. A node is submitted with "Full HTML" input format and the role
is granted edit permissions but the role only has permission to submit
with "filtered HTML" input format. The role will not be allowed to edit.