Good question. No idea.

In Thunderbird, I've just tested the 'Help' > 'Make a Donation' which normally opens on this link: https://donate.mozilla.org/en-GB/thunderbird/?utm_source=thunderbird-client&utm_medium=referral&utm_content=help-menu

But I'm getting a 404 page not found error.

The donate to 'Mozilla' link: https://donate.mozilla.org/en-GB/ That particular link does seem to be working - but that is Mozilla' and not 'Thunderbird'.

The Help > About Thunderbird aso has a donation link which is also going to wrong webpage.

There is a link to the correct webpage within Thunderbird If you select the account name in folder pane: On the right side near the bottom is 'about Mozilla thunderbird' and a load text which includes: The best way for you to ensure Thunderbird remains available is to 'make a donation' .

That particular link will open correctly here: https://give.thunderbird.net/en-US/?utm_source=start_page_tb_release&utm_medium=referral&utm_content=paragraph_text

Are you certain you donated to 'Thunderbird' or did you inadvertantly donate to 'Mozilla' ?

I donated to MZLA Technologies on the following web page: https://give.thunderbird.net/en-US/?utm_source=start_page_tb_release&utm_medium=referral&utm_content=paragraph_text

There is a dedicated support email address for donations. https://give.thunderbird.net/en-US/help/

A public forum is not the place to discuss credit card details. While the initial approach is via that web page, your replies and further interactions will be by email. My understanding is that donation processing is issue resolution is undertaken by Mozilla donor care under some form of contract with Mzla. But I have not been involved at that level for a number of years now.