Could not load file or assembly 'CrystalDecisions.CrystalReports.Engine'

If you receive an error message that says something like the following:

Could not load file or assembly 'CrystalDecisions.CrystalReports.Engine, Version=13.0.3500.0, Culture=neutral'

What causes this error?

This error happens when the SAP Crystal Reports Runtime installed dependency does not match the version required by Crystal Delivery.

This can happen if you upgrade Crystal Delivery, but did not update the runtime or if you previously have an older version of Crystal Reports Runtime.

How do I fix this?

1. Go to your Add/Remove Programs on your system.
2. Locate the SAP Crystal Reports Runtime application
   (It should look like this)
   
3. Click uninstall.
4. Re-install Crystal Delivery, and it will install the correct version of SAP Crystal Reports Runtime