It was able to load for me pretty quickly after looking into this. This is the screen you should see when it finishes loading:
Can you let me know which browser you’re using so I can test if this is a browser-specific issue? For example, sometimes Firefox doesn’t play nice with Wildbooks. It worked for me in Brave and Chrome.
Alternatively, you can try clearing your browser’s cache and cookies and then try merging the individuals again. This often helps address loading issues.