Looks like www.climateprediction.net replaced their TLS/SSL certificate with "Let's Encrypt" (lasting only 3 months at a time).

I'm getting an error saying, "The issuer certificate of a locally looked up certificate could not be found. No certificates could be verified." Can someone check this cert is publicly trusted?

OK, looks like the web admin forgot to install the intermediate certificate. The web server and its intermediate certificate are supposed to be sent to the client for TLS session setup.

See "certificate issues" here:
https://www.ssllabs.com/ssltest/analyze.html?d=www.climateprediction.net

I seem to have received these problem only briefly. Since that, only the usual return of no work available.

Tue 18 Apr 2023 09:24:00 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 09:24:00 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 09:24:02 PM EDT | climateprediction.net | Scheduler request completed: got 0 new tasks
Tue 18 Apr 2023 09:24:02 PM EDT | climateprediction.net | Project has no tasks available
Tue 18 Apr 2023 09:24:02 PM EDT | climateprediction.net | Project requested delay of 3636 seconds
Tue 18 Apr 2023 10:24:43 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 10:24:43 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 10:26:22 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 10:26:22 PM EDT | climateprediction.net | Scheduler request failed: SSL connect error
Tue 18 Apr 2023 10:26:24 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 10:27:50 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 10:27:50 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 10:29:50 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 10:29:50 PM EDT | climateprediction.net | Scheduler request failed: Timeout was reached
Tue 18 Apr 2023 10:29:52 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 10:31:56 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 10:31:56 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 10:33:16 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 10:33:16 PM EDT | climateprediction.net | Scheduler request failed: SSL connect error
Tue 18 Apr 2023 10:33:17 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 10:37:42 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 10:37:42 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 10:39:43 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 10:39:43 PM EDT | climateprediction.net | Scheduler request failed: Timeout was reached
Tue 18 Apr 2023 10:39:45 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 10:54:40 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 10:54:40 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 10:56:41 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 10:56:41 PM EDT | climateprediction.net | Scheduler request failed: Timeout was reached
Tue 18 Apr 2023 10:56:44 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 11:16:26 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 11:16:26 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 11:18:27 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 11:18:27 PM EDT | climateprediction.net | Scheduler request failed: Timeout was reached
Tue 18 Apr 2023 11:18:30 PM EDT |  | Internet access OK - project servers may be temporarily down.
Tue 18 Apr 2023 11:54:23 PM EDT | climateprediction.net | Sending scheduler request: To fetch work.
Tue 18 Apr 2023 11:54:23 PM EDT | climateprediction.net | Requesting new tasks for CPU
Tue 18 Apr 2023 11:55:40 PM EDT |  | Project communication failed: attempting access to reference site
Tue 18 Apr 2023 11:55:40 PM EDT | climateprediction.net | Scheduler request failed: SSL connect error
Tue 18 Apr 2023 11:55:43 PM EDT |  | Internet access OK - project servers may be temporarily down.
Wed 19 Apr 2023 12:23:16 AM EDT | climateprediction.net | update requested by user
Wed 19 Apr 2023 12:23:18 AM EDT | climateprediction.net | Sending scheduler request: Requested by user.
Wed 19 Apr 2023 12:23:18 AM EDT | climateprediction.net | Requesting new tasks for CPU
Wed 19 Apr 2023 12:23:20 AM EDT | climateprediction.net | Scheduler request completed: got 0 new tasks
Wed 19 Apr 2023 12:23:20 AM EDT | climateprediction.net | Project has no tasks available
Wed 19 Apr 2023 12:23:20 AM EDT | climateprediction.net | Project requested delay of 3636 seconds

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And also ssllabs.com reports a "Certificate name mismatch," https://www.ssllabs.com/ssltest/analyze.html?d=download.cpdn.org.

Wrong thread.