Hi Karen,
As you’re not the author of the vendor stores it won’t let you change the permalinks. I’ll investigate the capabilities I need to change to make it so the admins can actually edit everything.
I will be adding a vacation mode hopefully for the next release which should stop your need to change the store URLs. Version one of vacation mode will just be a store notice, version two will allow you to disable purchasing products from stores that are away.
cheers,
Jamie.