No Timer Displayed

I once used Easy Timer with no issues. Today I updated WordPress to version 4.4, then I put up a timer, and it won’t display, using this shortcode in a post:

[countdown date=2015/12/08-05:00:00]
[elapsed-timer]
[/countdown]

I’ve also tried using [elapsed-dhmstimer] and [timer].

https://wordpress.org/plugins/easy-timer/