Error: Unable to write object (Failed to reach API endpoint, got unexpected resp

I am using the cdn functionality. All was fine until a couple of weeks ago I think coinciding with installing Wordfence and now about every 24 hours the cdn stops transferring files and when I run the text I see this error message.

If I reauthorise and test all is fine and then it works for about another 24 hours and then stops again.

I tried uninstalling Wordfence (including forgetting all settings) and I tried upgrading to Wordfence pro so as to get a unique API but still I get this every evening (always seems to happe around 5pm).

Just wondering if anybody else gets this or knows why and what I can do.

Thanks very much

Joel