Email Notification Not Working

Notice: Trying to access array offset on value of type bool in /home/fumbleul/location-appartement-puy-st-vincent.fumble-ultimate.fr/libraries/kunena/external/nbbc/nbbc.php on line 3660

I am an new user to Kunena. I have set up my first forum and everything seems to work well in my testing except the system is not sending notification emails to my test users when a reply to a topic is posted. The Report Configuration is below. Any help would be greatly appreciated.

Notice: Trying to access array offset on value of type bool in /home/fumbleul/location-appartement-puy-st-vincent.fumble-ultimate.fr/libraries/kunena/external/nbbc/nbbc.php on line 3660

admin wrote:
I am an new user to Kunena. I have set up my first forum and everything seems to work well in my testing except the system is not sending notification emails to my test users when a reply to a topic is posted. The Report Configuration is below. Any help would be greatly appreciated.

Database collation check: The collation of your table fields are correct
Joomla! SEF: Enabled | Joomla! SEF rewrite: Disabled | FTP layer: Disabled |
htaccess: Exists | PHP environment: Max execution time: 30 seconds | Max execution memory: 256M | Max file upload: 64M
Kunena menu details:
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Joomla default template details : beez5 | author: Angie Radtke | version: 2.5.0 | creationdate: Unknown
Kunena default template details : Blue Eagle 2.0 | author: Kunena Team | version: 3.0.0 | creationdate: 2013-05-15
Kunena version detailed: Kunena 3.0.0 | 2013-05-15 [ Wanga ]
| Kunena detailed configuration:
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| Kunena integration settings:
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| Joomla! detailed language files installed:
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Third-party components: None
Third-party SEF components: None
Plugins: None
Modules: None