Greetings!
I have the same sodding problem: after I warp to
https://app.roll20.net/editor/ there is only black loading screen that never ends:

My specs via
http://supportdetails.com/ are:
Operating System Windows Windows 7
Screen Resolution 1680 x 1050
Web Browser Chrome 50.0.2661.102
Browser Size 1680 x 949
IP Address 194.135.17.120
Color Depth 24
Javascript Yes
Flash Version 21.0.-1
Cookies Yes
User Agent
Mozilla/5.0 (Windows NT 6.1; WOW64)
AppleWebKit/537.36 (KHTML, like Gecko)
I use Adblock and I can log into game only if I would use IP-proxy.
Console Log:
Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'self' 'unsafe-eval' https://*.googlesyndication.com https://*.doubleclick.net
https://partner.googleadservices.com https://www.googletagservices.com https://ssl.google-analytics.com https://www.google-analytics.com https://ajax.googleapis.com http://ajax.googleapis.com https://d3clqjduf2gvxg.cloudfront.net https://cdn.firebase.com https://*.firebaseio.com https://*.tokbox.com https://*.opentok.com
http://static.opentok.com http://www.google-analytics.com http://cdn.crowdin.com https://crowdin.com". Either the 'unsafe-inline' keyword, a hash ('sha256-flJTGS2QeIl8Y6e6qk6WahI/rpnTHa+EQQARhrpV1Ew='), or a nonce ('nonce-...') is required to enable inline execution.
app.roll20.net/:13 Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'self' 'unsafe-eval' https://*.googlesyndication.com https://*.doubleclick.net
https://partner.googleadservices.com https://www.googletagservices.com https://ssl.google-analytics.com https://www.google-analytics.com https://ajax.googleapis.com http://ajax.googleapis.com https://d3clqjduf2gvxg.cloudfront.net https://cdn.firebase.com https://*.firebaseio.com https://*.tokbox.com https://*.opentok.com
http://static.opentok.com http://www.google-analytics.com http://cdn.crowdin.com https://crowdin.com". Either the 'unsafe-inline' keyword, a hash ('sha256-j/BKvjJIk0Ivhw3IAc2xQKWrV+ZRiQyeIlGtPBx4j0k='), or a nonce ('nonce-...') is required to enable inline execution.
app.js:29 70
app.js:30 TOUCH SUPPORTED: false
app.js:30 USING WEBGL ACCELERATION...
app.js:30 WEBGL STARTUP SUCCESS
app.js:25 select
app.js:25 Switch mode to select
app.js:41 Initializing new dice engine with randomness...
app.js:41 Using random entropy
app.js:44 Compiling sheet...
app.js:44 Found rolltemplate: DnD35Attack
app.js:44 Found rolltemplate: DnD35Initiative
app.js:44 Found rolltemplate: DnD35StdRoll
app.js:44 Found webworker script
app.js:44 Custom Sheet Translation
app.js:44 Finding sheet rolls...
app.js:45 window resize
app.js:30 Final set zoom!
app.js:30 UPDATE GL SIZE!
app.js:30 Final set zoom!
tutorial_tips.js:7 tuts loaded
app.roll20.net/:1 Mixed Content: The page at '
https://app.roll20.net/editor/' was loaded over HTTPS, but requested an insecure image '
http://imgsrv.roll20.net/?src=i.imgur.com/A746uyc.png%3F1'. This content should also be served over HTTPS.
app.js?1464293223:45 window resize
app.js?1464293223:30 Final set zoom!
app.js?1464293223:30 UPDATE GL SIZE!
app.js?1464293223:30 Final set zoom!
sheetsandboxworker.js?20150218:237Starting up WEB WORKER
VM40:622•.¸¸.•*´¨`*•.¸¸.•*´¨`*•.¸ The Aaron Sheet v0.2.3 ¸.•*´¨`*•.¸¸.•*´¨`*•.¸¸.•
VM40:623•.¸¸.•*´¨`*•.¸¸.•*´¨`*•.¸ Last update: Thu Mar 03 2016 16:18:48 GMT+0200 (Восточная Европа (зима)) ¸.•*´¨`*•.¸¸.•*´¨`*•.¸¸.•
app.js?1464293223:36 Final page load.
app.js?1464293223:45 Refresh jukebox List!
app.js?1464293223:36 Scan for new plays!
http://imgsrv.roll20.net/?src=i.imgur.com/A746uyc.png%3F1 Failed to load resource: net::ERR_CONNECTION_TIMED_OUT