Hello:
I understand that you are the final user, with the images that you share, I can detect that your machine lost the corporate domain, for that reason it will never allow you to make the network password change.
To solve this problem you must ask the IT department, re-enter the computer to your corporate domain, the message that you send when you change the password "The server is not avaible.change your password when the server becomes available", is because it does not find the corporate domain and you will never find it, until you reconfigure the Mac.
As a recommendation you have to make a backup of your account information, since when entering the domain, a new account may be created.
Your user account is operated locally, and you have a connection to the network services, since the network is structured with corporate dominoes
This problem could be caused since the equipment was not configured correctly
I recommend once the Mac is entered into a domain, change the password connected via Ethernet (the WiFi service must be turned off), so that the change replicates correctly
This information can be useful for your IT department
https://support.apple.com/kb/PH26282?locale=en_US&viewlocale=en_US
I hope with this you can solve the problem,you can edit the post and remove the network images if you wish
Regards
