Hi @AhmadF.Cheema, thanks for taking the time to report this!
Has this been already brought up on https://www.mediawiki.org/wiki/Project:Support_desk ?

No, sorry, should I have done that first?

Reported it on support desk at: https://www.mediawiki.org/wiki/Topic:T7po6uisor9f7nz0 too

Solved (kind of).

Just tried a new test install:
MediaWiki 1.28.0-alpha (b8804f6)

• This time the number of recent contributors (or {{NUMBEROFACTIVEUSERS}}) was stuck at -1 instead of 0. This reminded me of an old MediaWiki bug.
  • T56888
  • T22017
• T22017 indicated a temporary fix using:

php maintenance/initStats.php --active --update

• Because of the change in the maintenance .php file, used the following command in SSH:

php maintenance/initSiteStats.php --active

• This fixed the issue.
• However, it should be pointed out that I had previously run multiple times:

php maintenance/initSiteStats.php --update

• which didn't help. It did update the other variables (like number of edits etc.) but not the number of active users.

• Created another test account, to see if the number was updating now automatically or not.
• It wasn't. Had to run "initSiteStats.php --active" again to update the value.
• Tested again to repeat the results and make sure there wasn't a jobs backlog problem.
• There wasn't. The issue is persistent and unable to be fixed without running: "initSiteStats.php --active".

I can confirm this happens in my wiki after upgraded to MW 1.27.1.

In my case all active user (number in special:statics, api result, and {{NUMBEROFACTIVEUSERS}}) number stuck in the number where it been updated last time. Manually run php maintenance/initSiteStats.php --active or php maintenance/UpdateSpecialPages.php are the two only way to get active user number change.

Check the "Active Users and Users" session in https://wikiapiary.com/wiki/Moegirlpedia_(zh) . The active users number stuck at 1030 after Oct23, at 899 after Nov18.

Hope the patch were include in MW 1.27.2 as well as the master version.

(User number counting were not affected)

@Aklapper I am new to the bug reporting system; @Bawolff I just tried running MW 1.30 with $wgMiserMode = false defined, but there was no effect on getting the statistics to update itself again. :-(

In T140079#3978573, @Marianian wrote:

@Aklapper I am new to the bug reporting system; @Bawolff I just tried running MW 1.30 with $wgMiserMode = false defined, but there was no effect on getting the statistics to update itself again. :-(

Yes, because the bug is present when $wgMiserMode = false; (The default). The bug will go away if miser mode is true and you run updateSpecialPages.php in a cron script once a day, but that's probably not a very good solution for most people.

We encounter a new error in MW 1.31.
The active user number droped from 1.3k to 50 after php /var/www/wiki/maintenance/rebuildall.php .

Neither php maintenance/initStats.php --active --update nor php maintenance/UpdateSpecialPages.php fix the number count error. However, the Special:ActiveUsers page do show all 1.3k editors' name at the same time.

$wgMiserMode = false / true doesn't seem to affect the active users number anymore this time. It's always 50.

In T140079#4772255, @Zoglun wrote:

We encounter a new error in MW 1.31.
The active user number droped from 1.3k to 50 after php /var/www/wiki/maintenance/rebuildall.php .

Neither php maintenance/initStats.php --active --update nor php maintenance/UpdateSpecialPages.php fix the number count error. However, the Special:ActiveUsers page do show all 1.3k editors' name at the same time.

$wgMiserMode = false / true doesn't seem to affect the active users number anymore this time. It's always 50.

This looks like a different problem. Please create a new task for this