Uncaught referenceerror jitsimeetexternalapi is not defined: single user

I have a pretty robust jitsi network working fine with octo, multiple videobridges and web servers, have had several hundred people on it in multiple rooms at the same time. (azure cloud ubuntu 18.04 with nested traffic managers and all that stuff.) I have a single, important, user getting: uncaught referenceerror jitsimeetexternalapi is not defined I am assuming they are using a VPN tunnel, but am told it does not work when they turn it off. Just wondering if anyone knows the cause of this symptom already, guessing I am not the first to come across it in this scenario.