Thank you, I've just done that.
Will wait to see if it helps.
Just for interest, the error message in the log is as follows:
2019-04-19 18:35:11 - App Warning: AbanteCart core v.1.2.13 Warning: Accessing store with non-configured or unknown domain ( mail.tjn.co.za/ ).
Check setting of your store domain URL in System Settings. Loading default store configuration for now. in /home/tjncoza/public_html/core/lib/config.php on line 228
The store URL setting is set as:
Store URL:
http://www.tjn.co.zaSecure Store URL:
https://www.tjn.co.za