How to update formula in a column that has reference from another sheet and I added new data points


I have a reference formula in a column that picks up information from another sheet. I recently added more data to the this other sheet. My reference formula column isn't picking up the new data points.

Reference Sheet:

country Name country Code

United States US

Canada CA

I added Germany and Australia to Country Name column and Country Code

My sheet where I have formula isn't showing AU or DE for when the Country Name column in that file has Australia or Germany. Why would that be?