Listings page is blank on new directory install

I just set up the Directory plugin on a multi-site installation. Added a couple listings to get the hang of it. Did the settings, etc. But the listings page is blank - as in php error blank. Other pages, e.g. add-listing and my-listings work fine.

I tried:
1. Turned on WP debugging - only picked up a notice (which I doubt has anything to do with it and may be left from the change in version 4+):
Notice: Use of undefined constant WPLANG - assumed 'WPLANG' in /home/massmatch/domains/ on line 57

2. Changed theme to Twenty Fifteen
3. Network disabled all plugins except Directory and the WPMU dashboard
4. Checked error log for the site - nothing