Sharepoint - Unknown issue

I understand that it can be frustrating to experience issues with SharePoint, especially when it's a part of your onboarding process for new employees. I'll try to provide some steps to help you troubleshoot and potentially resolve the issue. Please note that some of these steps might require SharePoint admin privileges. 

1. Check Microsoft 365 Service Health: Verify if there are any ongoing issues or incidents with SharePoint or related services on the Microsoft 365 Admin Center (https://admin.microsoft.com). You can find the service health information under the "Health" section. 
2. Verify sharing settings: Ensure that the sharing settings in the SharePoint admin center are still configured correctly. To do this, go to the SharePoint admin center (https://<your-domain>-admin.sharepoint.com) > More features > Sharing > check the sharing settings for your organization and the specific site you're trying to invite users to. 
3. Review User Licenses: Make sure the users you're trying to invite have the appropriate licenses assigned. You can check this in the Microsoft 365 Admin Center (https://admin.microsoft.com) > Users > Active users. 
4. Check SharePoint permissions: Verify that you still have the necessary permissions to invite users. You can check this by navigating to the SharePoint site > Settings (gear icon) > Site permissions. 
5. Test with another user: If possible, ask another user with similar permissions to try inviting new starters to the SharePoint site. This will help you determine if the issue is specific to your account or a wider problem. 
6. Review Azure AD settings: Check your Azure AD settings to ensure there are no recent changes or issues related to user provisioning. You can access Azure AD through the Azure portal (https://portal.azure.com) > Azure Active Directory. 

I hope this helps!