Change WordPress user roles and capabilities › Forums › Restrict or Permit access inside WordPress – how to › Serious problem with user not able to edit content blocks. Settings are correct. › Reply To: Serious problem with user not able to edit content blocks. Settings are correct.
Btw, ‘mu’ is too short for the role ID. You may use the role name ‘MU’, but I do not recommend to use such short string for the role ID. I saw a code (from plugin or even WordPress core) where user role was checked this way: if string with current user roles and capabilities contains a needed role ID. Imagine what it may find if it will check just for the ‘mu’ occurrence.