Hi Elaine,
Oh shoot, sorry for the trouble here with the radio buttons in the ticket fieldset!
Would you be willing to expand the settings for the radio buttons from the screenshot you shared? I tried creating some myself on a default WordPress installation like you (Twenty Sixteen, no other plugins) and all seemed to work (screenshot), but let’s see if your field settings are different from mine (screenshot) and narrow this down from there.
I also happened to notice that you are running Events Calendar PRO 4.2.1 and there is a newer version available. Would you be willing to update to version 4.2.2.1 (download is available here on this site in your account)? That shouldn’t have an impact here, but I’d like to rule that out just in case.
Thanks!
Geoff