Roaming Captive Portal does not load Cascading Style Sheets (CSS).
Roaming Captive Portal authenticates every web request, including those to content delivery networks (CDN's). The requests to the CDNs are not recognized by the site because they redirected from a URL other than that of the CDN. This will result in Cross-Origin Resource Sharing (CORS) errors and the content from the redirected requests will not load.
The Authentication Bypass list cannot function to circumnavigate the CORS issues with Roaming Captive Portal.
The best solution is to implement the Unified Agent (UA) access method for mobile users.