We run an old version of Oracle that runs specific versions of Java and higher versions of IE do not support them AIUI. We also have to run in Compatibility Mode with IE 10 lol.

For those that will stumble upon this thread as I have:

These also run on W7 as we have the same problem. Windows 7 is the latest OS we can use for Oracle due to the support of IE10. Sometimes I...

You could certainly reinstall 8.1 and upgrade again, activating and trying a clean install after that. I don't see how you could become "unblocked" without contacting MS. I've had to do that with an...