Hello there and welcome to the Wowza support forum.
You may need to enable access to the advanced administrative settings:
Enable access to advanced administrative settings
If you notice in the "Users" page that you do not have admin access you will need to edit the /conf/admin.password file. It should look like this:
From there you should be able to Enable default properties
# Admin password file (format [username][space][password][space][group]|[group])
#username password group|group
username password admin|advUser
I hope this is helpful.