flightaware.com/live/flight/UAL9 … /KIAD/LSGG
But only because I’m on today’s flight 
We do not receive specific reasons from the airlines for their diversions or cancellations. Chances are it was due to weather or maintenance, but thankfully everything seems to be on schedule for today’s flight.
flightaware.com/live/flight/UAL … /KIAD/LSGG
You can also contact United to see if they have any further details. 1-800-864-8331.
I hope you have a great flight!
Considering the cancellation afterwards, it was almost definitely mechanical.