Best answer by Anonymous
Thanks for posting! We've had reports that this issue has affected a number of our customers. It looks like it may be an issue with our server and the Tech team are now aware of this.
You should still be able to view the graphs via the My OVO app on a smart phone and in some cases refreshing your My OVO page online resolves the issue. If you've tried refreshing a couple of times and it isn't working - try again in a couple of days.
Let me know how you get on.
** Updated 11/07/2019** More info here.