This error happens due to a bug, it happened for me as well. When you are assigning  only read rights to a single role, it happens.  Just check the checkbox “Allow creating new object” and “Allow Deleting New Objects” It will save. Later on, you can uncheck it and save.

Thank you very much Shekhar. It finally works.

After I checked this two boxes, I managed to save it.

Hey there,
if i am reading your problem correctly, you are following all the steps from the learning path, but an error is preventing you from actually saving that setting.

could you share a screenshot of your problem? and a screenshot of the settings you selected?

here is screenshots of the error. 

Hi Namie,

I think this is caused because you don't have any attributes yet on the Teacher entity. Add an attribute, for example ‘Name’ and try to do the same thing. Then you can set read or reat / write for that attribute. After that you will be able to save.

Hi,

I have the same problem, and I can not fix it.

I have attributes on the Teachers entity, but still not working. I received the same error message.

Ensure that you tick in the box “read”