When We Will Get Participation Certificate Appathon 2023?

Its been almost 3 months and I still didn't
get the participation certificate. When I will get it?

Certificates were issued mid-August and everyone was asked to get theirs from their participant portal. Is there any reason why you did not do this at the time?
I will check with our Dev Team to see if anything can be done this late in the year.
Why don't you send an email to appinventor@mit.edu with all your Appathon info and I will start the request process.

I did went to the portal. I only got 3rd place people's choice award certificate. There was no other certificates than the people's choice award.

Only people who received no other honor received participation certificates. Having won 3rd place in the people's choice category implies participation!