We use a custom domain, organisation.my.salesforce.com
A couple of users this morning reported on of our apps was not working. When I logged in and tested, it looks like all custom Visualforce pages served from the organisation--c.visualforce.com/ are just giving a DNS error message (DNS_PROBE_FINISHED_NXDOMAIN)
Initially I thought this was an internal network issue, but I have tested via tethering my machine to a 4G connection, and am still getting the issue.
All of the managed packaged pages are working - for example Finacialforce, which pages have a URL format of organisation--ffc.visualforce.com are working fine.
I have raised a case with Salesforce support, and they have started 'working' on the case a few hours ago, but I've heard nothing from them, apart from an email saying this is a developer issue and we should consider purchasing a support plan.
I've checked the Setup Audit trail, and none of the other administrators have made any changes in the last 24 hours.
Am I missing something, or is this clearly a Salesforce infrastructure issue?