FYI: Gotcha with OneDrive Settings > Regional Settings interface ...

FYI in case someone else strikes this. I could not save changes to the Regional Settings until I realized that the OK and Save buttons were hidden behind the Settings panel. Once I hid the Settings panel by clicking the gear icon I could see and click the OK button (see images below). 

I know that this is probably a very noob thing but happy to get that tag if it saves another noob a bit of time. :)

And never really understood why the OK and Cancel buttons were placed on the far right of settings pages but ...

Ian.