SCC now use Microsoft MyApps to publish the internally hosted system e.g. POS.
To access this browse to myapps.microsoft.com and sign in with your SCC account (same account you currently use to access D365)
Once signed in you will see a list of applications you have been granted access to,
to access the PO System or overtime simply click on the icon, and you may be prompted for the username and password again, this again is your SCC one.
any problems please email it.support@scc.com