What is your environment language and what language do you want a dictionary for? What is the URL that you can't access?

Hello Thanks for the reply

I work and build my OS in french and I would like to add the Italian and Brasilian portuguese languages in thunderbird.

The inactives (for me) urls are: For the italian : https://addons.mozilla.org/thunderbird/downloads/latest/3053/platform:2/addon-3053-latest.xpi?src=dp-btn-primary

and fr the portuguese : https://addons.mozilla.org/thunderbird/downloads/file/260240/verificador_ortografico_para_portugues_do_brasil-2.4.1-3.2-an+sm+fx+tb+fn.xpi?src=dp-btn-primary

I tryed just now but are inoperating ...

well, to pursue, I can manually download the two dictionaries. I saw somewhere in the past a manual procedure to add dicionnaries in thunderbird, I will try to do it.

Adding the dictionnaries from thunderbird do not work

The URL opened in Thunderbird when going to Edit > Preferences > Composition > Spelling > Download More Dictionaries is https://addons.mozilla.org/en-US/thunderbird/language-tools/. It opens fine for me in Thunderbird or in the browser.

You're right when clicking on the dictionary nothing happens in Thunderbird.

I was able to save the corresponding XPI and install it manually, though.

I was able to download both Italian and Brazilian Portuguese XPIs, perhaps try again later.

Me too,, as I wrote before, but the dictionaries arn't 'loadable" from thunderbird. I add a print scrint attached of the non funcitonning page. I will try to add them manually. Do you know the procedure to do it in thunderbird?

You have to open that same page in the web browser : right-click anywhere on the page > Open in Browser.

Done Many thanks Schuss Gil