Committing changes doesn't commit changes

[Brooke Herbert]

I have just recently installed source tree on a new laptop.  I am attempting to do a simple commit.  After staging my files and entering a commit message I select commit in the bottom right corner, a popup appears to enter my user details for the commit.  Once I select ok the dialogue box closes and nothing is committed. If I run a commit through the terminal window it works fine. 

This is with version 3.3.9 on Windows 10.