Preview not working with wordpress using addon domain

Hello,

I have set wordpress up as follows:

– wordpress is installed at http://www.mydomain.com/wordpress
– using an addon domain: http://www.travelswithmybike.com

I have set up the following in Settings/General
WordPress Address (URL): http://www.mydomain.com/wordpress
Site Address (URL): http://www.travelswithmybike.com

The site works fine for public access. By that I mean I can access the site, view blog posts, and all links work.

What does not work is if I try to preview a draft post.

I have a draft post, when I look at the link for “Preview” it is: http://www.travelswithmybike.com/?p=16&preview=true

What happens is I get a page with the URL:
http://www.travelswithmybike.com/?p=16
and a message: OOPS! THAT PAGE CAN’T BE FOUND It looks like nothing was found at this location. Maybe try a search?

I have just upgraded to WordPress 4.9.4.
I am using the Twenty Seventeen theme.

I suspect the issue is with the addon domain.

I am fairly new to wordpress, had installed it many years ago, and never really found a use for it until I wanted to set up this particular blog.

Does anybody have a similar setup, who has encountered this issue and overcome it?

Any input gratefully received.

thanks,
margie