If you are having issues with the Merge Request Review Overview section not loading please do the following:

In the Project General Setting go to the Merge Request section, expand. Make a change - any change - and save. Revert the change and save.

Compare Git revisions

To see what's changed or create a merge request, choose a branch or tag (like master ), or enter a commit (like 4eedf23 ).
Changes are shown as if the source revision was being merged into the target revision.