Cloudflare flexible ssl and mupx

I have deployed my app using mupx.

I have added cloudflare nameservers and enabled flexible ssl option. I have enabled force ssl package, and set https:// in route url. It still does not work.

I get
SSL connection error ERR_SSL_PROTOCOL_ERROR

What else should I do?
Thanks.

Edit : I could not find the solution. Therefore bought ssl certificate