If you are not seeing the option to add an Excel Web Access Web Part under the Business Data Category:
Make sure to enable Custom Script under Admin > SharePoint > settings >
The new “Custom Script” (no-script) feature
Turn scripting capabilities on or off
As you can see, if this is disabled, you will not be able to add an Excel Web Access Web Part.
Also make sure the blew features are enabled:
1. Activate SharePoint Server Enterprise Site features (Site settings > Manage site features under Site Actions):
2. Activate SharePoint Server Enterprise Site Collection features (Site setting > Site collection features under Site Collection Administration):
IMPORTANT NOTE: After making these changes it could take 24 hours for the changes to appear.