If you are having trouble viewing your website content from a specific network, this can indicate that the network has been configured to use an internal DNS structure.
To troubleshoot this, try accessing your website from your smart phone while your wi-fi is switched off in your phone's settings. If you are able to load your website successfully, there is probably an internal issue on your network that needs to be resolved. Visitors outside of your office's network should be able to view your webpage just fine. If the internal DNS structure has a specific record entered for your domains that isn't matched to the records listed in your domain manager for your connected HubSpot domains, the request from your website browser to the hosting server (HubSpot's server) will not be able to complete.
To verify whether your network is using an internal DNS configuration you'll need to reach out to your network engineering team. If your network does use an internal DNS structure you will need to pass that team your HubSpot assigned CNAME records from the domains manager and have them update the records in their configuration. Your IT Team may also need to flush the DNS cache.