Hi Miss Veronica,
I have solved the problem. It was a setting in UM that was wrong, and has now been fixed. Thank you for taking the time to get back to me about this.
Hi Abwaita,
Yes, I forgot that the site is like that. But that turns out to be the problem!
After doing more plugin tests, I found that the login and registration plugin itself was causing the malfunction, it would just not let Woocommerce show the selection of how many items to order. I have had to uninstall it and re-build a login and registration system for the site!