So if you have seen this error:
We're sorry. We ran into a problem completing your request. Please try that again in a few minutes.
Believe me even if you tried again in few minutes it might not work...
Check in central admin if your excel services is running.
Check if you have an Excel Service application in your service applications.
In Central Administration
Go to Application Management
And then in Manage Web Application
I select my web site (Share Point - 80) and then select 'Service Connection'
Finally I Checked Excel Service Application And it work for me.