We had an issue on our machines today where we had to do a system back-up (24 hours), thus meaning machines had to be re-installed with UE4.
Now after download has completed and we get to verifying stage, installers just get stuck on 90%. It has been around an hour now. I’m wondering is there a reason for this?
It sounds like you might be experiencing this issue:
Can you take a look at solution listed there and see if it helps you? If not, feel free to update that answer with any details you can.