The rollout of Chrome version 63 is causing a conflict with the outdated and soon-to-be-updated WebRTC library that is currently being used by Roll20.
This conflict causes the loading of the virtual tabletop to hang and stall out completely. There are two ways to avoid this currently:
Before WebRTC initializes (meaning the sole Game Master is alone in the interface), going to My Settings and disabling internal Video/Audio.
Utilizing Firefox as your browser for the time being.
We will have an update to help mitigate this problem early within the week, and beyond that have an overall fix for WebRTC voice and video coming to the Development Server very soon.
Our apologies for not properly anticipating the scope of this Chrome issue in advance of the gaming weekend.