Attempting to import the sites fails with the red error invalid credentials and a reference number.
The following is required for successful validation of the credentials:
1. Validate and make sure the user id and password are correct.
2. The OneDrive password must be typed in the box and not pasted because pasted content is just entering the asterisk characters not the actual text password i.e. **********.
3. Sometimes we get this error if the password contains special characters, in this situation, change your password removing special characters.
4. Sometimes we get this error if administrator is using SSO for Office 365\Sites login during the activation flow. CASB\CloudSOC don't support SSO in the activation flow.
5. If none of the above works export the site list from sites and import the sites, as there is no need of providing user id/password. For steps see: Article 175925 - Manual import of sites during MS Office 365 Securlet activation
6. Please ensure you have followed the Article ID: 175597 - Prerequisites for activating the Office 365 Securlet
7. If none of the above resolve your issue please refer to Article ID: 171265 - Error "Invalid username or password" when activating Office 365 securlets
NOTE: There is no difference between methods to active sites while Office 365\Sites - both login and CSV will active updated list of sites in organization.