Weird Cert issue when calling webhook from shell

[randomCodeNoob]

Got an server on the internet with a let´s encrypt certificate for the https-application, running Apache2
Have installed webhook. Set up webhook id and script, tried to call the webhook-id from an application, got cert errors.

When i call the webhook url or webhook-id urls in Browser ( https://my.webhook.server:9000 ) Browser shows my valid let´s encrpt cert (tried multiple Browsers).
But trying with curl, this happens:

root@otherserver:~# curl -vvI https://my.webhook.server:9000
*   Trying XXX.XXX.XXX.XXX:9000...
* Connected to my.webhook.server (XXX.XXX.XXX.XXX) port 9000 (#0)
* ALPN: offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/certs/ca-certificates.crt
*  CApath: /etc/ssl/certs
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS alert, unknown CA (560):
* SSL certificate problem: unable to get local issuer certificate
* Closing connection 0
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.`

This is the running service:

root@webserver:/etc/webhook# service webhook status
● webhook.service - Small server for creating HTTP endpoints (hooks)
   Loaded: loaded (/lib/systemd/system/webhook.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2024-02-14 15:00:34 CET; 1s ago
     Docs: https://github.com/adnanh/webhook/
 Main PID: 17522 (webhook)
   CGroup: /system.slice/webhook.service
           └─17522 /usr/bin/webhook -nopanic -hooks /etc/webhook.conf -secure -cert /etc/letsencrypt/live/my.webhook.server/cert.pem -key /etc/letsencrypt/live/my.webhook.server/privkey.pem

Feb 14 15:00:34 webserver.stratoserver.net systemd[1]: Started Small server for creating HTTP endpoints (hooks).
root@webserver:/etc/webhook#

Any idea what is going wrong here?

[adnanh]

Could this be of any help? https://community.letsencrypt.org/t/why-does-curl-not-trust-letsencrypt/183585