SharePoint owner checking out an Excel spreadsheet shows as Read Only. Only happening to user

Hi,

I have a uses who as 'Owner' permissions.

When they open Excel files from a Shared Folder, which requires to be checked out for editing, which is set in the versioning settings, then states it's Read Only??

It only seems to be happening to the particular user.

I've removed them from the group permissions and added them back in, as they have recently changed roles, which I wouldn't of thought that would matter??

As anyone else experienced this with a user and have you resolved it?? 
Is there something potentially wrong with their actual profile or setting in Excel itself that is causing this?

Regards

Chris
would there be a setting