Based on the suggestion from Slack support team, analysing the Safari console output during the issue had following error related to websockets:
[Error] WebSocket connection to
'wss://wss-primary.slack.com/?token=xoxc-123131232101-83721934891-031941234108-
1230492lsajendf98u244lnwdfo19284u83u12ndsflae1220233dpodf01921lkd&sync_desync=1&slack_client=desktop&start_args=%3Fagent%3Dclient%26org_wide_a
4&enterprise_id=E10ASDLK1230&batch_presence_aware=1' failed: WebSocket
is closed before the connection is established. close
(gantry-shared.d106548.min.js:1:136366)
_closeSocket (client-boot-imports.477648b.min.js:1:1886117)
This gave a hint on to look for issues related to Safari and websockets specific to Monterey. With this exploration, following forums/threads had useful information on WebSockets issue related to Safari post macOS 12.2 upgrade:
So, based on the discussions in the above listed pages, there are two causes of websockets failure in Safari in macOS 12.2.1:
NSURLSession WebSockets's inability to process split messages normally.
NSURLSession WebSockets requests compression by including the Sec-WebSocket-Extensions: permessage-deflate header, but ignores when the server responds as not supporting it, and continues assuming the connection is compressed.
The common solution suggested is to disable experimental feature NSURLSession WebSockets:
(macOS 12.2.1) Safari (Menu) -> Develop -> Experimental Features -> NSURLSession WebSockets (Untick to disable this experimental feature)
After disabling NSURLSession WebSockets in Safari now Slack is working as expected, the new messages load automatically and also notifications were sent for the new messages.
Also, the bug comment states that: This issue should be fixed in an upcoming iOS 15.4 Beta and macOS 12.3 Beta.
Load new messages
link, it doesn't show the new messages.NSURLSession WebSocket
from macOS 12.2, and as per this thread the issue is being fixed as part of macOS 12.3.