When adding the OLC course in the Student records > Achievement > Completed courses 
Error 400 - "Value for parameter NonParticipation StatusID is not valid with the provided CompletionStatusId". 
The error indicates that the Non Participation Status value is not valid with the Completion Status. 
Check the Student Record > EQAO accommodations > OSSLT 
- Non Participation Status 
- Completion Status 

In the case that the Completion status is Not Reported and the participation status is Deferredyou need to change the Completion status for Not applicable - that allow us to change the participation status for None specified.   

Once the course is added to the student records, go back to the Student Record > EQAO accommodations > OSSLT  and change the Completion status.