Can't use aggregation function when assigning column to 'Values' in matrix.

Hi there,

I can't seem to access the aggregation function when assigning a column to the 'Values' section of the matrix visual. I have tried other colleagues' dashboards and they can do it. I will try to demonstrate the issue below:

I have IDs from Test which I add as Rows as seen below

I want to add country so that it goes next to each ID as it corresponds on the Test table. When I try to drag Country to the values section it just doesn't work. I have done the exact same test on a collegues computer and it works. 

What I am trying to do:

My collegues computer:

Have I changed a setting? I have also noticed that none of columns have the Sigma symbol next to it. (Like ID in the screenshot of my collegues computer). I have also reinstalled Power BI and had no such luck.

Thanks in advance for the help!