Looks like you have everything correct. May be a bug then because this forum looks to be reporting something similar. Looks to be in larger courses mostly. Sorry I couldn't help more.
Happy
oodling!
Looks like you have everything correct. May be a bug then because this forum looks to be reporting something similar. Looks to be in larger courses mostly. Sorry I couldn't help more.
Happy
oodling!
This is a quiz so your Review Options may be the cause for the hide icon. You mention that there are no start/end dates. My guess is you have Marks checked in the Immediately after the attempt section but have it unchecked in the Later, while the quiz is still open and After the quiz is closed sections. Can you take a screenshot of the Review options section located at the bottom of the quiz's settings page?
Happy
oodling!
Happy
oodling!
Did the teachers enter a Post date that hasn't been reached yet?
There are three dates set when creating a Turnitin assignment: Start Date, Due Date and Post Date.
There should be a little plus "+" symbol after the roles that are left with that permission. Click that and you will be given the option to add back a role to that permission. Make sure not to select the plus symbol that is underneath Prohibit; that will take away access.

Note: Above example is screenshot from my Moodle instance. I have custom roles added that you may not have on your site.