For the embedded shopfronts to work your site needs to be HTTPS and not HTTP. This is for the extra layer of security, encryption and authentication which is really important when dealing with data etc.
If you look at your website hosting provider they may have an option to upgrade at a relatively reasonable price. In general it’s worthwhile exploring, especially if you’re collecting user data and wanting to take payments through it - there may also be GDPR implications for needing to do this too (not my forte but worth bearing in mind).
To note Google has also changed its algorithms recently to give preference towards https:// websites over http:// ones, it will also start notifying users that a website is “not secure” from October 2017:
“Starting October 2017, Chrome (version 62) will show a “NOT SECURE” warning when users enter text in a form on an HTTP page, and for all HTTP pages in Incognito mode.”
An alternative option which I’ve heard about but not too familiar with is a free option of getting HTTPS onto your site through a software called Lets Encrypt, apparently we use it here (@Lynne.OFN.Tech are you familiar?) . This is the website: https://letsencrypt.org/