The update function runs on a crontab. It can take a while before updating.
If you dont want to wait you can do the following:
You can enable debug mode and force the update. Otherwise just wait.
Go to wp-content/plugins/jsdelivr-wordpress-cdn-plugin/ and open the file jsdelivr.php
On line 39 set true.
Example: protected $debug = true;
Save and upload. Go to dashboard to the plugin page and press the "Help" button on top. Press "Check for Update".
Done