I used the BOINC 7.16.20 x64 for a long time. Recently I could not download new Rosetta tasks. Then I updated the BOINC to 8.0.2 version. The Rosetta and other projects worked OK, except the Einstein@Home one. I posted to E@H forum a topic about this problem, but nobody could give a proper solution. So I reversed using the BOINC 7.16.20 version again, because you and some other people can fix the problem of “no downloading Rosetta tasks”.
I am not an IT so I don’t know where to find /etc/Hosts on Windows and how to fix it.
Could you please help me.

To edit the Hosts file, follow these steps:

Open Notepad as Administrator:
Search for "Notepad" in the Windows search bar.
Instead of left-clicking it, right-click on Notepad and select "Run as administrator"
When the dialog box pops up select Yes

To open the Hosts File: In Notepad:
Go to File > Open.
Navigate to C//Windows/System32/drivers/etc which will appear empty
Change the file type filter from "Text Documents (*.txt)" to "All Files".
Select the "hosts" file and click "Open"

Edit the Hosts File:
On a fresh line at the bottom, type
128.95.160.156 boinc-files.bakerlab.org
Save the file

That should be it.
No need to reboot.
Return to Boinc manager, select Rosetta and click the "Update" button.
Cross fingers

Following your instruction, I got the Rosetta tasks downloaded.
Thank you, Sid Celery!

This change in the host file worked in my case for my linux system! Wow! For 3 months no crunching and now it works again.
However I do not understand at all, why such an entry in the hosts file ist necessary at all...

The method for Android works!

I know where to find /etc/Hosts on Windows. But on Android, I have no idea...

You can install personalDNSfilter from F-Droid, and add a custom rule (e.g. host entry). personalDNSfilter filters DNS requests sent from your phone, it can also modify DNS response so your phone get 128.95.160.156 when it lookup boinc-files.bakerlab.org .

Here is a screenshot of the page where to make the adjustment:


The two units obtained after the unblocking ended in error but it seems that they were bugged because they ended in error with another cruncher...
Since then, I have obtained other units that seem to work well.

PersonalDNSfilter is available on F-Droid as KaguraMea said, but also on the Play Store for the less adventurous.

I hit this issue on Linux yesterday. The actual problem is that the SSL connection to boinc-files.bakerlab.org doesn't send enough of a certificate chain by itself to ensure validity; specifically, the issuer certificate for boinc-files.bakerlab.org isn't generally present in the system's list of trusted certificates. Because of this, OpenSSL will consider the certifcate to be invalid, because it can't verify the certificate chain. (Firefox, on the other hand, when opening that URL in a browser, seems to accept it, possibly because it's separately fetching the issuer certificate and validating that.) This error can be seen by running the following command on Linux systems:

openssl s_client -connect boinc-files.bakerlab.org:443

The proper fix is to send the issuer certificate for boinc-files.bakerlab.org (similar to what's being done for boinc.bakerlab.org); this requires the system admin/webadmin to make changes. One alternative fix that can be done locally (instead of modifying the /etc/hosts file) is to add the issuer certificate (InCommon RSA Server CA 2) into the system's list of trusted certificates. On Linux, this can be done by the following:

wget http://crt.sectigo.com/InCommonRSAServerCA2.crt
openssl x509 -in InCommonRSAServerCA2.crt -out InCommonRSAServerCA2.pem -outform PEM
sudo cp InCommonRSAServerCA2.pem /usr/local/share/ca-certificates/InCommonRSAServerCA2.crt
sudo update-ca-certificates

The first command downloads the certificate. The second command converts it from the binary CRT form to the hex-encoded PEM form. The third command copies it into a system-local ca-certificates directory (it hopefully exists by default). The fourth command updates the /etc/ssl/certs/ca-certificates.crt file with all of the trusted certificates.

The method for Android works!

Here is a screenshot of the page where to make the adjustment:

This looked simple enough even for me to install, but...
On the page you've taken a screenshot of, how is the file saved?
I exited out of the page with no save prompt and re-entering the page removed the line. Repeatedly.

You can safely assume I'm a complete idiot - no offence will be taken

---

The method for Android works!

Here is a screenshot of the page where to make the adjustment:

This looked simple enough even for me to install, but...
On the page you've taken a screenshot of, how is the file saved?
I exited out of the page with no save prompt and re-entering the page removed the line. Repeatedly.

You can safely assume I'm a complete idiot - no offence will be taken

You're not stupid, it's me who didn't think of this possibility... 😅

Indeed, by closing the application directly, the line disappears. *well seen*
Just go back to the application's home page by clicking on "Advanced settings" to save, then click on "Restart" to activate. 😉

The method for Android works!

Here is a screenshot of the page where to make the adjustment:

This looked simple enough even for me to install, but...
On the page you've taken a screenshot of, how is the file saved?
I exited out of the page with no save prompt and re-entering the page removed the line. Repeatedly.

You can safely assume I'm a complete idiot - no offence will be taken

You're not stupid, it's me who didn't think of this possibility... 😅

Indeed, by closing the application directly, the line disappears. *well seen*
Just go back to the application's home page by clicking on "Advanced settings" to save, then click on "Restart" to activate. 😉

You over-estimate me - I have blind-spots.
Ok, I did that and it seemed to stick. Good.
I tried to draw down some Rosetta tasks but none arrived - I'll let it try again of its own accord and hope things go well.
Many thanks for making this so easy after all this time - my fingers are crossed.

---