The reason "The Block" is not on tonight is due to a scheduling decision related to external events or programming shifts. Generally, the show airs at 7:30 PM on Channel 9, but the schedule can be impacted by big events like sports or special broadcasts. For example, in one instance, the show was not aired on a particular night due to the NRL Grand Final, causing no episode to be shown and related activities like judging to be postponed until the next day.

Additionally, there can be production and event-related changes such as the cancellation of the public Open Day for safety and logistical reasons. This decision affects fan interaction but does not necessarily affect the TV broadcast schedule directly.

If for today the block is not aired, it is likely due to such scheduling or event-related adjustments on Channel 9. For the most accurate and up-to-date information, checking the local TV guide or Channel 9's schedule for tonight is recommended.