How can I force HTTPS on my third-party domain without .htaccess?

[surewaydm]

I have my domain with namecheap and my ssl too. However, when I check the https://www.whynopadlock.com/  I get the notification:

Your webserver is not forcing the use of SSL.
You may want to add a redirect to ensure a secure connection is used

Shopify doen't allow access to .htaccess what is my other option?

[Sox]

It might have been a temp problem if it happened within 48 hours of updating the A record to point to shopify - seee https://help.shopify.com/en/manual/domains/managing-domains/secure-connections.