Unable to log in with WebId-TLS

[Sheap]

When testing the login flow using WebId-TLS, I was unable to successfully log in using my certificate.

I configured the certificate such that it points to my pod in the subjectAltName, and added the public key information into my pod settings, all as outlined here

When I try using it to log in from firefox or chrome directly, I get this error:

Class constructor URL cannot be invoked without 'new'

When I try using the client certificate in postman to retrieve a private file, I receive a 401 response. (I'm not sure if this use case would even be expected to work, but I wanted to rule out browser issues)