LHC, WCG, Milky Way, Einstein, Cosmology, Rosetta are working fine.

They do not check stuff like this project does or so I have read.

I assume you downloaded the correct file as listed by Keith.
From reading your listing, that file was put at d:\Program Files\
it should have been put at d:\Program Files\boinc

just move that file into the proper folder and restart boinc

[edit]
From the command prompt do a file compare to verify the missing old cert

fc ca-bundle.crt ca-bundle.crt_old

There's a line

10/6/2021 3:54:11 PM | | [http] [ID#0] Info: SSL certificate problem: certificate has expired

which conforms that BOINC (note spelling) is still using the old ca-bundle.crt file. I don't buy the 'cached' explanation: the 'path' explanation is possible, but unlikely.

LHC, WCG, Milky Way, Einstein, Cosmology, Rosetta are working fine.

They do not check stuff like this project does or so I have read.

Yes they do, but they use certificates from a different supplier - and they're still working.

But the file location definitely needs sorting out.

Problem resolved.

I had replaced the ca-bundle.crt file in D:\Program Files\BOINC, but I missed replacing it in D:\Program Files

After replacing ca-bundle.crt, in D:\Program Files, everything is fine now.

Apologies for messing this up and thanks for the help.