It looks like your access group roles do not grant you write permissions to the Data-Admin-Systems-Settings class.
What are the roles listed on your access group? Can you check to see if any of those roles lists the Access Class Data-Admin-System-Settings with the Write instances column set to your production level?
Your system may be locked down and you may need to contact an administrator.
As a side note, I moved your post to the Pega 7 Platform area of the PDN forums. The Pega 7 Express > Support forum is specific to Pega 7 Express and this feature is not exposed in Express.