I have received an email from Envato saying this:
Fix the certificates in your demo: https://envato.d.pr/HMeWKC/1tv5xF73DG
Question 1: Does it mean that our template has only one issue which is certificate error and rest is okay?
Question 2: To fix this error, I just need to get a SSL certificate?
First you should solve this issue then reviewer will mention what are the errors you have in your template. Once you fixed the errors, reviewer will accept your template.
Okay. Thank you so much for your help.
I doubt they will have reviewed the item at all based on that message
I think the mentioned issue is the intro issues. after you fix the issue and submit the update then reviewer will go through the review process. if your site running inder https then you should run with a secure ssl certificate.
Okay. Thank you. 
Yeah, we are installing SSL certificate. After this we will re-submit the template. Thank you for your help. 