Looking at previous posts, it may be that LucidChart is having a temporary outage. I just don't see evidence on their status page yet. (https://lucidsoftware.statuspage.io/)
I can provide more logs, but here is a sample of the errors I get in Chrome's Dev Console:
Access to XMLHttpRequest at 'https://analytics.lucidchart.com/sessionActions' from origin 'https://www.lucidchart.com' has been blocked by CORS policy: Request header field user is not allowed by Access-Control-Allow-Headers in preflight response.
VM440:1 POST https://analytics.lucidchart.com/sessionActions net::ERR_FAILED
(anonymous) @ VM440:1...