I was mentioned in this message while I was not in the chat room. Usually, this should become a notification after 15 minutes.
However, I didn't get any notification as can be seen in this screenshot:
As you can see, I do get notifications from comments and from chat rooms in Stack Overflow.
Also, this is not the first time. For long time I don't get notification from the chat room mentioned in the link above, while I do get notifications from Stack Overflow room. Possibly a bug?
Referring to: https://scifi.meta.stackexchange.com/a/939/31259
Point 3 looks like the answer to your question because you got pinged with '@ber':
@Ton will notify you if you've been in the room in the past two days and there's no other user for whom this would be a better match, e.g. someone called "Ton" who has been there within the past seven days (that's 1.) or someone called "Ton Ynnuf" who has been there within the past two days (that's 2.).
Based on the transcript, you hadn't been in the room for 2 days, so no notification.
Thanks to @JoErNanO's advice, I logged out and logged in back, and tested it again with @JoE and @Sha, and I started receiving notifications again.
