Well... I really asume this is an FAQ but I don't know why.

Anyone can teach me about that? I cannot add Minecraft via boinccmd or UI on Windows 11 of BOINC manager/client

What have you tried, what error are you getting?

You could try using
boinccmd --project_attach https://minecraftathome.com/minecrafthome/ <account key>

You can find your account key here
https://minecraftathome.com/minecrafthome/weak_auth.php

You could try this as well
boinccmd --lookup_account https://minecraftathome.com/minecrafthome/ <Email address> <password>

Have you checked Logs to see what's happening?

Just to reiterate that you also have to spell the URL correctly, the first half has 'at' while the second one doesn't
https://minecraftathome.com/minecrafthome/

I cant add the project either on Windows or Linux machines.
Using url https://minecraftathome.com/minecrafthome/
Asks me to enter my username and password, then tells me project added successfully.
However nothing happens from there on, log says,
27/09/2025 11:34:34 PM | | Fetching configuration file from https://minecraftathome.com/minecrafthome/get_project_config.php

It would appear as though it fails to retrieve the config and doesnt get added to the boinc project list.

+1 to the above

Same, cannot attach project.

Turns out it was due to their anti spam software. The issue is fixed now

I cannot see the project is listed in BOINC manager UI
https://photos.app.goo.gl/CgXq46ZVEp2sFW6i9

Is that normal?
Meanwhile, several days ago, I cannot attach project via boinccmd shell command on both Linux or Windows. But today it looks okay now.

However, I checked C:\ProgramData\BOINC\all_projects_list.xml
and /var/lib/boinc-client/all_projects_list.xml

There is no Minecraft stuffs inside. I supposed that could be the root-cause that why UI cannot see Minecraft. Somebody removed Minecraft stuffs in all_projects_list.xml?[url][/url]

Can confirm working correctly, was able to add project.