Bibliography not in alphabetical order Word 2019

Hi everyone,

I've recently finished a dissertation and noticed that, unlike with my PC, Word for Mac will not automatically organise my citations by alphabetical order in the automatic bibliography. No matter what referencing style I use. I know it may not sound bad, but when you have a load of citations you don't want to be putting them in order manually. What's strange is that the citations panel on the right does put them in alphabetical order. Any clues??

Thank you!