Post Code as Geography Data Type - 37 out of 88 not recognised

[chandelirious]

Hi, as the title says really.

I have a data set of 88 postcodes. They are local schools, so well established buildings in well established areas.

I need to plot these on a map in Power BI, so I've gone to Data toolbar in Excel and clicked on Geography. Out of the 88 postcodes, 51 of them have the small map icon showing that they are recognised as valid post codes. However, 37 of them have a question mark.

They are all formatted in exactly the same way.

How can I solve this? I've searched online and not found anything helpful.

I'm using Office 365, trying in both the browser version and desktop version of Excel.

Appreciate any help on this!

Thanks in advance.