Prerequisites
Browser support
We support every browser that Atlassian officially supports in its products. More information.
Exceptions:
The mobile view in the confluence app is not supported. Also the desktop version in mobile resolution is not supported, but may work with restrictions.
Confluence
Please make sure that you are logged into SharePoint Online with the same Browser, otherwise you will see the following error:
Check 3rd Party Cookie configuration (if login does not work)
Please make sure your Browser accepts 3rd party cookies, to be able to see SharePoint content in Confluence, else you might get the error above despite being logged into both applications with the same browser.
In case you don't want to allow third party cookies in general it would also be an option to just whitelist the following domains:
[*.]microsoftonline.com
[*.]atlassian.net (it would also be possible to just whitelist your Confluence Cloud domain directly)
Also check any privacy apps or blocker extensions installed in your browser if you get the above error messages.