I checked the forum and many people are complaining about the same issue of being requested "additional documents". Here is what one of the replies says. I guess people found it on the IRCC website:
"We are currently experiencing very high traffic on our online services. You may have difficulty accessing them. We are working to resolve this issue.
- If you are unable to submit a document on time as a result of the technical difficulties, try again over the next few days. If you are concerned about missing your deadline, submit the requested documents using the IRCC Webform.
- You may see an incorrect application status asking for a medical exam or additional documents. If you actually need to send any documents or do a medical, you will see a message in your account and a letter explaining what you need to do."