Hello Mate, Have a nice day!
 
After you change logo and favicon(or any of the configuration) in Admin -> Stores -> Configuration -> General -> Design -> HTML Head and Header
You need to refresh the cache if you activate them in Admin -> System -> Cache Management -> select All Cache and Submit “Refresh”
Please view screen shoot below:
http://screencast.com/t/GgvIISzb
 
Tell us if your problem unsloved
Thank’s!