Getting “concatenate xmlrpc” error with Total Synchronization

I’m looking for ways to clean up metadata in our media library and develop a better system of media management. I have been hoping that by using WP/LR to synch with the media library, I could use Lightroom to manage the metadata, clean up image titles and alts etc.

I have Lightroom CC set up, along with the WP/LR plugin in WordPress (vers 4.7), and am able to upload images to WP from Lightroom with no problem.

However I am unable to get Total Syncronization to work, I’m getting the following error in the WP/LR log on my computer:

12/31/2016 11:29:04 TRACE Throttling: Pause for 30 seconds.
12/31/2016 11:29:34 TRACE WPLRSyncAPI.config.url: https://www.liveside.net/xmlrpc.php
12/31/2016 11:29:34 TRACE Loading XMLRPC lib
12/31/2016 11:29:34 ERROR Response: “wplr.lrplugin/WPLRSyncAPI.lua:51: attempt to concatenate field ‘xmlrpc’ (a nil value)”
12/31/2016 11:29:34 TRACE Check connectivity to Google.com
12/31/2016 11:29:34 TRACE Check connectivity to https://www.liveside.net/xmlrpc.php
12/31/2016 11:29:35 ERROR Connection to your website works but got an error from WP. (…)

This happens both with the Lightroom plugin set to REST, and to XMLRPC. Earlier I was getting some errors due to not enough memory allocation, but I’ve upped the memory in my test site and that seems to have fixed that error, however I’m still unable to get past the error screen when trying to load Total Syncronization.

We are a independent news blog, with lots of images. Will this plugin even work for my intended use?
I am using the plugin as a trial (set to FREE in Lightroom), I will happily pay if I can get it to work (and may well indeed use it even if it’s just to upload from LR), but it would be awesome to be able to use the capabilities of LR to manage our photos and metadata.

Thanks so much.