Hello,
I had exactly the same problem. The SoundCloud page was called up, I logged in and then nothing came up except "Redirecting..." and StudioOne waited forever. Then I took a closer look at the request and saw that the redirect links to a URI SCHEME, which was not added in the registry for me - under Windows. That's why it couldn't work.
In this case, the following text should be adapted accordingly, the whole thing packed into a file with the extension ".reg" and then called up under Windows:
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\studioone]
@="URL:StudioOne OAuth2 Protocol"
"URL Protocol"=""
[HKEY_CLASSES_ROOT\studioone\DefaultIcon]
@="D:\\Audio\\StudioOne6\\Studio One.exe,1"
[HKEY_CLASSES_ROOT\studioone\shell]
[HKEY_CLASSES_ROOT\studioone\shell]
[HKEY_CLASSES_ROOT\studioone\shell\open\command]
@="\"D:\\Audio\\StudioOne6\\Studio One.exe\" \"%1\""
The only important thing here is to adjust the path to the StudioOne application accordingly. After double clicking the file, you had to confirm before continue...and that's it.
Hope this would help you 8-)
Marc