SimpleIndex does not support multi-factor authentication to connect to a SharePoint Online site that implements it.

If your admin has set up 2-step verification for your organization you’ll need to generate an app password so the app can connect to Office 365.

Once you have an app password, you use this in place of your original password with SimpleIndex to connect to the SharePoint site. Your SharePoint administrators should be able to create one for you.

You can find more information about App Password here:

https://docs.microsoft.com/en-us/azure/multi-factor-authentication/end-user/multi-factor-authentication-end-user-app-passwords

For instructions on how to set one up, visit this page:

https://support.office.com/en-gb/article/Create-an-app-password-for-Office-365-3e7c860f-bda4-4441-a618-b53953ee1183