Are you using the right syntax?

On enwiki it's {{ping|username}}... You're seemingly using wikilinks? [[सदस्य:George Ho|George Ho]] is that supposed to work?

@Reedy, yes, the {{ping}} etc templates are just a shortcut. Only a direct userpage link is required, plus a few other technical requirements, per https://www.mediawiki.org/wiki/Manual:Echo

I've made 2 test pings to Jayprakash12345 at https://hi.wikiversity.org/wiki/%E0%A4%B8%E0%A4%A6%E0%A4%B8%E0%A5%8D%E0%A4%AF_%E0%A4%B5%E0%A4%BE%E0%A4%B0%E0%A5%8D%E0%A4%A4%E0%A4%BE:Quiddity_(WMF)

If the second test didn't work, then I suspect the cause is something to do with the localized "User" namespace name.
If the first test didn't work, but the second did, it's probably cause by something to do with Jayprakash12345's custom signature. (I forget exactly how this gets complicated. Possibly templatized signatures?)

So we need a Lua module to do this?

https://hi.wikiversity.org/wiki/Module:Reply_to

That is not needed. Also the {{ping}} template was not used in the original failed mention.
I've sent 4 more tests to you, in case you're eager to debug. ;-)

In T174873#3576250, @Quiddity wrote:

@Reedy, yes, the {{ping}} etc templates are just a shortcut. Only a direct userpage link is required, plus a few other technical requirements, per https://www.mediawiki.org/wiki/Manual:Echo

I've made 2 test pings to Jayprakash12345 at https://hi.wikiversity.org/wiki/%E0%A4%B8%E0%A4%A6%E0%A4%B8%E0%A5%8D%E0%A4%AF_%E0%A4%B5%E0%A4%BE%E0%A4%B0%E0%A5%8D%E0%A4%A4%E0%A4%BE:Quiddity_(WMF)

If the second test didn't work, then I suspect the cause is something to do with the localized "User" namespace name.
If the first test didn't work, but the second did, it's probably cause by something to do with Jayprakash12345's custom signature. (I forget exactly how this gets complicated. Possibly templatized signatures?)

No Notification I get.

I tested

• mentioning on hi.wiversity with the original failed mention, changing only the usernames. The mention successfully came.

• Checked {{ping|username}} worked for me too. A username was in English.

• Also, checked cross-wiki notifications - worked too.

@Quiddity After your testing do you have some cases of mentions that did not get through?

Also, for further investigation on the issue, I suggest to turn Preferences-Notifications Failed mention/Successful mention option on to clearly see if mentions are failing to be sent.

@Etonkovidova I've added 4 tests pinging you, at https://hi.wikiversity.org/wiki/%E0%A4%B8%E0%A4%A6%E0%A4%B8%E0%A5%8D%E0%A4%AF_%E0%A4%B5%E0%A4%BE%E0%A4%B0%E0%A5%8D%E0%A4%A4%E0%A4%BE:Quiddity_(WMF)#Test_Pings
I've also confirmed with Reedy that he did not receive the pings I had sent him earlier (he looked at Special:Notifications and nothing was listed locally).
I also didn't get any success or failure of mention-notifications.
All very weird!

It looks like the namespaces are all as they should be. (I looked at InitialiseSettings.php)
I've tried sending myself another ping, and got nothing.

Next, someone should check the production DB.

Are there any recipients that sometimes work and sometimes don't?

@Quiddity I did some testing today - interestingly that many test cases initially trigger mention notifications:

For all cases - mention were added on a blank page and the user signature is just inserted (not modified in any away)
What worked:
(1) Mention ::[[सदस्य:Etonkovidova|Elena] Sir, Thank you --[[सदस्य:Zilant17|Zilant17]] ([[सदस्य वार्ता:Zilant17|वार्ता]]) २३:१६, १३ सितम्बर २०१७ (IST)

(2) two mentions - only one comes
Hi {{ping|Etonkovidova}}, test 3 --[[सदस्य:Zilant1|Zilant1]] ([[सदस्य वार्ता:Zilant1|वार्ता]]) २३:२१, १३ सितम्बर २०१७ (IST)

Hi [[User:Etonkovidova]], test 4 (now with success/failure mention preference turned on...) --[[सदस्य:Zilant1|Zilant1]] ([[सदस्य वार्ता:Zilant1|वार्ता]]) २३:२१, १३ सितम्बर २०१७ (IST)
(3) ping mention
Hi {{ping|Etonkovidova}}, test 5 --[[सदस्य:Zilant13|Zilant13]] ([[सदस्य वार्ता:Zilant13|वार्ता]]) २३:३०, १३ सितम्बर २०१७ (IST)

(4) a usertalk spaces in hindi
Hi [[सदस्य वार्ता:Etonkovidova]], test 6. --[[सदस्य:Zilant63|Zilant63]] ([[सदस्य वार्ता:Zilant63|वार्ता]]) ००:१०, १४ सितम्बर २०१७ (IST)

(4a) userspace, not usertalkspace
Hi [[सदस्य:Etonkovidova]] test --~~~~

(5) multiple users are mentioned:

Hi [[User:Zilant1]], test 1. --~~~~
Hi [[User:Zilant17]], test 1. --~~~~
Hi [[User:Zilant63]], test 1. --~~~~ ---- does not receive!

After the above tests - the mentions stopped coming; the mention notifications from different wiki for the test users would come, but not for hiwikiversity.

I'll do more testing tomorrow.

To summarize the testing results:

• The notifications from previous tests were not identified as mention notifications, only as updates to the user talk page.
• Testing today - no mention notifications ever came, not even as notificaitons updates on a page (as previously).
• Mention notifications (the same tests) work on other wikis.

The issue is confirmed.

Hello All. This is a Hindi Month. half month going, only 13 days left.

Users are reporting the same kind of issue on ptwiki. For example, I didn't get a notification from this edit:
https://pt.wikipedia.org/w/index.php?diff=50111696

He7d3r: Please comment on T177825 instead.

It seems that the fix in T177825: No on-site Notifications received for certain type of actions solved the problem of not sending mentions, so I am closing the bug.