OneDrive business not loading - No blue cloud in system tray

Howdy,

I have setup 4 user's laptops (Windows 10) on our new Office 365 Business Standard package.

All laptops use the same email address for Microsoft personal & business accounts.

(we get the prompt "Work/School or Personal" when accessing Microsoft online)

According to a Microsoft support person this is what they are encouraging now.

3 setups work perfectly, have both blue & white clouds in the system tray (for business & personal files) with "OneDrive" and "OneDrive - <our domain name>" folders in explorer and c:\users\<username>.

1 laptop is refusing to load OneDrive business.

No blue cloud in system tray.

No "OneDrive - <our domain name>" folder in explorer or c:\users\<username>.

I have tried reinstalling OneDrive (from https://www.microsoft.com/en-au/microsoft-365/onedrive/download)

I have tried reinstalling Office 365 (from www.office.com)

No change.

I haven't tried the "Add an account" button in the OneDrive personal settings yet.

Could this work?

Help please!