You need to start subscription service, which is must for installing apps in SharePoint environment.
If you didn't already created subscription service use ps to install one,
New-SPSubscriptionSettingsServiceApplication -ApplicationPool "SharePoint Web Services Default" -Name "Subscription Settings Service Application" -DatabaseName "SubscriptionSettingsDB" | New-SPSubscriptionSettingsServiceApplicationProxy
To be on safe side, try this ps script,
$subscriptionSettingsService = Get-SPServiceInstance | where {$_.TypeName -like “Microsoft SharePoint Foundation Subscription Settings Service”}
if($subscriptionSettingsService.Status -ne “Online”) {
Write-Host “Starting Subscription Settings Service”
Start-SPServiceInstance $subscriptionSettingsService | Out-Null
}
else{
Write-Host “Subscription Settings Service was already started”
}
while ($service.Status -ne “Online”) {
# delay 5 seconds then check to see if service has started sleep 5
$service = Get-SPServiceInstance | where {$_.TypeName -like “Microsoft SharePoint Foundation Subscription Settings Service”}
}
If it's truely running then try PS to add Appdomain and url,
Set-SPAppDomain “apps.com” –confirm:$false
Set-SPAppSiteSubscriptionName -Name “app” -Confirm:$false
Reference