and in fact my Boing installation is not uploading anything since then.
thanks for sharing the new certificate once available.
all my warmest regards to everybody

Dear, thank you for your advice,
I did it twice, downloaded directly form BOINC website, it was not helpful…
don't know what else to do.
it worked perfectly until Xmas eve… I just noticed today that I have tens of "Universe@Hone" tasks "pending".. conversely, other projetcs works fine and regularly upload results.

... I just noticed today that I have tens of "Universe@Hone" tasks "pending".

Universe@home has been having sever problems on and off since around 12/24. Right now the website is unreachable.

Those completed task will eventually upload once the project gets the server working, however long it may take. Due to the heavy COVID-19 cases in Poland the university hosting the project may be short staffed also.

If just one projects cannot upload, it's usually down to the project having problems with its servers. Check if their website is there, check their forums.
Since Universe's website doesn't load for me, you can easily assume it's their problem and you'll have to wait until they return. No number of redownloading and reinstalling of BOINC will fix an external project going broken and not contactable. It happens at times.

Edit: Also keep an eye on the New on Project Outages thread at the top of this forum, in it people will report whether a project is up or not. Universe was reported as missing on January 2nd.

But there are so many different flavours of Linux, and so many different implementations of BOINC, that it's hard to give general advice.

I think though that any Linux system that is updated regularly will stay up to date enough on this. (once a month is easily enough.)

Dears,
many thanks: I wait.
in the meantime I'm not wasting CPU cycles.
I will check in a few days if the server come up again then and won't bother you anymore.
many thanks again.
I wish all of you a wonderful 2022.
Andrea

Universe@home probably won't be back on line until end of month, they had a MAIN SERVER HARD DRIVE CRASH... see my post linked below in Project Outages:
https://boinc.berkeley.edu/dev/forum_thread.php?id=10279&postid=106682