Hi @ADubichev , please follow the valuable instructions from @justinburch. it happens some time. Give a try on the following methods
1. If you are accessing portal from your organization internet. Make sure to check the proxy settings and whitelist the url. Or switch it to different wifi and give a try
2. Try a hard refresh which is ctrl + f5 together
3. Try in incognito window without anyadblockers on the browser
Please post the result here
Hope it helps
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