Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
It produced this output:
nginx: [warn] "ssl_stapling" ignored, no OCSP responder URL in the certificate "/usr/local/etc/letsencrypt/live/truenas/fullchain.pem"
nginx: [warn] "ssl_stapling" ignored, no OCSP responder URL in the certificate "
My web server is (include version): nginx v 1.20.1
The operating system my web server runs on is (include version):TrueNAS-12.0-U5.1
My hosting provider, if applicable, is: self
I can login to a root shell on my machine (yes or no, or I don't know):yes
I'm using a control panel to manage my site (no, or provide the name and version of the control panel):
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot):1.18.0
I would try removing the last cert from the fullchain.pem file and restart nginx.
If that workaround fixes the problem, you will have to switch to using the alternate trust path chain.
If it does NOT fix the problem, please show the nginx vhost config file that serves that FQDN securely.