SMS and Outlook 365

[AC Question]

Phone sends SMS messages to my Outlook 365, which I want. Set up online outlook 365 to be able to respond to forwarded sms messages as per MS webite, and it worked from my desktop app. But as soon as I shut down the online version of outlook 365 the desktop is no longer able to reply. How can I get my desktop outlook to be able to reply if onone version is not open?

Devices S8, Windows 10, Outlook 365 - all fully updated