CentOS Linux 7.9.2009
Hi All,
We have a WP site that does regular imports via cron. It stopped working. We thought that may have been an conflict issue with the plugin and the newest version of WP, contacting the plugin vendor for assistance. The assumption was because the day it stopped working was the day we backed up the virtual site and updated WP. However, Let’s Encrypt also updated that day, and running the job manually revealed the issue that the jobs were running but failing because it couldn’t authenticate the Let’s Encrypt cert. This hadn’t happened in the last year we’ve been running, so I’m at a loss how to fix it? And visiting the site via browser the cert returns valid. 
This is the error:
WARNING: cannot verify www.wannagohome.com's certificate, issued by '/C=US/O=Let\'s Encrypt/CN=R3':
Unable to locally verify the issuer's authority.
I’ve added -no-check-certificate to the wget cron command until I can resolve this issue.
https://www.wannagohome.com - you can see the cert is valid according to the browser.
Thank you for any advice or assistance.
-Ron