Unfortunately, as many of you will have noticed, there is a bug in the current release (3.0.1) which causes the ticket form either not to show at all within single event pages or else be replaced by some error messages.
Please first of all accept our apologies for this oversight: we are planning on delivering a maintenance release that fixes this shortly.
In the interim, please refer to the advice in the following thread – either of those workarounds should resolve this until the maintenance release arrives.
https://theeventscalendar.com/support/forums/topic/errors-on-all-event-pages/#post-56826
Thanks!