I think you still have time to process your PCC application. I searched on Google, and TET will start from Jan. 25 to Feb. 2. Start processing your PCC request as soon as possible. I got my PCC 20 days after including a public holiday too. In case you run out of time, gather all evidence that you've applied for it, and send those as proof along with a letter requesting an extension of your deadline. Explain the national holiday coming up in Vietnam and the expected date you can submit the document. You can also call IRCC and ask for advice directly.