The Subscription Settings service and corresponding application and proxy needs to be running in order to make changes to these settings.

If you are getting the above error after following all the steps from internet to create an APP and still not able to create it on your share point. You are at the right place because I also had the same problem. Solution is given as under:

$manaccount = Get-SPManagedAccount SPS-2012\Administrator
Remove-SPServiceApplicationPool -Identity SettingsServiceAppPool
$appPoolService = New-SPServiceApplicationPool -Name SettingsServiceAppPool -Account $manaccount
$appService = New-SPSubscriptionSettingsServiceApplication -ApplicationPool $appPoolService -Name SettingsServiceApp -DatabaseName SettingsServiceDB
$proxyService = New-SPSubscriptionSettingsServiceApplicationProxy -ServiceApplication $appService
Follow the above given commands and use them on your share point command prompt. Replace the SPS-2012 with your computer name. if you are not sure or you don’t know the name of your user used in share point services. Use the under given command to check the account name.
Get-SPManagedAccount

Now the real solution of the problem is to restart your IIS after performing all the steps given above. after restarting the IIS go to central administration and you will see the proxy and other services running to create an APP.