This happens to me quite intermittently.

I had a Project with a colon in it as the name

NZ COR: Project 1

I get the 404 error message when clicking on this link.
I changed it to
NZ COR - Project 1

And it worked
Then changed it back to
NZ COR: Project 1
and 404, then changed it back to
NZ COR - Project 1

and still 404.

Seems to affect old projects before a release last week.
Newer projects don't seem to cause this 404.

I solved this isssue by restarting php-fpm process... It seems after upgrade, some old codes are still run in php-fpm process, we should restart it by this command:

/etc/init.d/php-fpm restart