Same here, we are getting the following errors when trying to acces TestFlight Tab:
HTTP500: SERVER ERROR - The server encountered an unexpected condition that prevented it from fulfilling the request.
(XHR)GET - https://itunesconnect.apple.com/testflight/v2/providers/<provider_id>/apps/<app_id>/platforms/appletvos/trains
HTTP500: SERVER ERROR - The server encountered an unexpected condition that prevented it from fulfilling the request.
(XHR)GET - https://itunesconnect.apple.com/testflight/v2/providers/<provider_id>/apps/<app_id>/platforms/ios/trains
HTTP500: SERVER ERROR - The server encountered an unexpected condition that prevented it from fulfilling the request.
(XHR)GET - https://itunesconnect.apple.com/testflight/v2/providers/<provider_id>/apps/<app_id>/testInfo