Certain activities such as view/edit records require that CloudExtend users be logged directly into NetSuite with a web services connection. Other actions, such as attaching emails and creating records only require that a user be logged into NetSuite in a browser session.
If you're receiving a prompt to enter your NetSuite credentials it means that the action being performed requires a web services connection. Simply enter your NetSuite credentials to continue. Note that support for signing in with roles that require SSO or two factor authentication are not yet supported.