Microsoft add-ins are web apps, ie they run inside a browser. The combination of your operating system and Outlook version is used by Microsoft to determine which browser the add-in is managed in (Edge or Internet Explorer (IE)). Note, this is irregardless of the browser you use on a day to day basis and CloudExtend does not control which browser Microsoft uses. Learn how to determine which browser is used here.
Some users have their browser set to clear cache whenever the browser is closed. If this setting is applied to the browser used by CloudExtend (IE or Edge) then this will force you to login on a more frequent basis. To avoid this set your browser to not clear cache on exit.
Microsoft Edge instructions
Privacy and Security
Choose what to clear
Make sure that cached images and files is set to off
Microsoft Internet Explorer instructions
Make sure that delete browsing history on exit is NOT checked