The same problem for, me.
On completely fresh installation of WordPress 4.2.3, Duplicator version 0.5.22 it works well, but on my install it does not work.
I made some tests, and here are my observations:
1. This problem is theme independent. In step 2 “Back”, “Rescan”, “Next” buttons and checkmarks are not visible. Tried with my own theme, TwentyTwelve, Thirteen and fifteen as well. No luck.
2. This problem is plugin independent. Removed all plugins used in installation (except duplicator ofc), the same results.
3. The only difference between working fresh installation and non working, plugin free, standard theme one is couple of pages and posts added.
Conclusion:
So, I couldn’t find problem source. In my case, I installed fresh WP 4.2.3 and took current database from existing older vesion of WP. After installation WordPress said that database needs to be updated, which i did without any problems. In my opinion this WordPress database upgrading is an issue. It cant be anything else, as I said, I made my non-working installation as close to fresh as possible – no plugins, standard theme.
I will try to solve this on my own, but hope this helps!
Cheers!