Learning Locker - connection refused

Hi, I'm trying to connect our version of Opigno to Learning Locker. I've followed the steps in the manual and have the LRS Stats menu appearing on the Statistics page. However, when I click into these stats I get the following warnings: "An error occured while requesting Learning Record Store data (Connection refused)" The recent log messages report that the response could not be sent, but doesn't give much more information. I'm pretty sure I've put the correct Learning Locker details (endpoint, username, password) into Opigno. (Have checked with Learning Locker support and they confirmed that "they've tested querying with those credentials and we are not seeing an issue"). For the endpoint, I've tried with a trailing slash and without, both with no luck. I've flushed caches, run cron etc but still can't get a connection. If you could give any possible ideas/help that would be really appreciated. Also if there's any more details I can give, let me know. (Not sure how to attach screenshots of errors/logs) Thanks!