Not surprising .... iThena.Measurements & iThena.Computation are timing out with SSL errors.
Either the main web site is under high DDOS attack or they are having server problems again.

12/18/2021 19:04:29 | iThena.Measurements | [http] HTTP error: Couldn't connect to server
12/18/2021 19:04:29 | iThena.Measurements | Temporarily failed upload of ***: connect() failed
12/18/2021 19:05:54 | iThena.Measurements | [http] Info:  Unknown SSL protocol error in connection to root.ithena.net:443
12/18/2021 19:05:54 | iThena.Measurements | [http] HTTP error: SSL connect error
12/18/2021 19:05:54 | iThena.Measurements | Temporarily failed upload of ***: transient HTTP error
12/18/2021 19:05:54 | iThena.Measurements | Backing off 00:07:26 on upload of ***

Or they are using one of the two SSL certificates in the BOINC client bundle (yes, the emergency fix v7.16.20 version) which expired on 15 December.

They are:
GlobalSign
Cybertrust Global Root

Can you reach the iThena website via a secure SSL browser? If so, what does the browser say about the ceritifcate status?

Edit - as I warned in https://github.com/BOINC/boinc/issues/4530#issuecomment-933664532

Both are pulling up fine for me using HTTPS and iThena.Coputational is connecting correctly via 17.16.20 on this PC

Bill F

It's back working on all my PC's with latest BOINC program.

The SSL ERROR MESSAGES for iThena come and go without warnings.

It has gotten worse since their hosting provider had that massive fire at their main data center earlier this year that destroyed lots of hosting infastructure. Not sure if that has anything do with it.

The two projects hosted off the main website are recording on average 200 to 300 new fake "users" each day but only a handfull of new computers. I have asked the project admin several times to implement some kind of registration capthca or email verification without success. That would greatly help the DDOSing of the project server(s).

If the Project staff can't be bothered to protect the project your concerns are way down on the List. Of course when you get a message notification you can't click on the Link you get a big red 404 error indicating that there government provider does not like it.