Installation of OpenCart using Installatron not working

I have installed 3.0.3.8 in a sub-folder of web root using tsoHost's Installatron package. No warnings.

A LetsEncrypt certificate is installed and https works fine on my static content in web root. When I try to access the OpenCart install at https://kerryscakes.com/order I'm told that the connection is insecure (and a response code of 301). OpenCart renders, but as text. If I disable protection (in Firefox), OpenCart renders fine, but over http not https. See attached image.

I got some help from the LetsEncrypt community and they noticed that:

The URL: https://kerryscakes.com/order/ produces content that contains "http://" 88 times!
You need to remove the HTTP from the code. It should be self-referenced.
The first occurrence starts the ball rolling in that wrong direction: <base href="http://kerryscakes.com/order/" />

Is the problem with the tsoHost installer? What can I do to fix the install?

Thanks for any advice
Seb

What do your configs look like? All have httpS?

You may want to read this thread: viewtopic.php?t=226983