There are few reasons why you might see this error after uploading your course. 

Incorrect Tool:

Currently ReviewMyElearning supports Articulate, Captivate, Lectora, and iSpring.

imsmanifest.xml not in root of zip:

The SCORM specification states that the imsmanifest.xml should be in the root folder of the course. See the last paragraph of this article: Content Packaging

SCORM Package Zip:

The course should be zipped after being published for SCORM. Most tools will offer to this for you and that is the best method. If you need to zip the course by hand ensure you do not simply right-click the published folder and compress it. 

  1. Open the published folder
  2. Select all the folder contents (ctrl-a)
  3. Right-click a file.
  4. Select "Send To"
  5. Select "Compressed (zipped) folder
A short video on how to zip the files: