We're sorry. We ran into a problem completing your request. Please try that again in a few minutes

If you insert your Excel Web Access and then you choose the workbook from a trusted document library you may have this error:
We’re sorry. We ran into a problem completing your request. Please try that again in a few minutes.

to fix this issue

1.   Open Central administration

2.   Application management

3.   Manage web applications

4.   Select the web application where your site 

5.   Manage service connections

6.   Select the Excel Services Application

7.   Click OK

if your have already configured your Excel Services (ref: http://technet.microsoft.com/en-us/library/jj219698(v=office.15).aspx) Everything will be OK.

Enjoy...