I noticed when I run the check manually on available updates page no longer work for quite a while even if I updated the core manually once. It keeps showing the following message.
Failed to get available update data for ... projects.
May I know how to fix this.
There have been similar issues reported in the forum - mostly due to expired certificates. This happened to me back in October with my local environment.
Check this and see if this helps:
https://forum.backdropcms.org/forum/issues-checking-updates-localhost