Try to run the cURL command on your linux servers' shell but without the silent flag and with additional output:
curl -Lv https://domain.tld/filename.txt
Then you'll see what happens and you'll get the HTTP headers + response code aswell
Found the error. SSL Error
Initializing NSS with certpath: sql:/etc/pki/nssdb
* CAfile: /etc/pki/tls/certs/ca-bundle.crt
CApath: none
* Server certificate:
* subject: E=
[email protected],CN=Plesk,O=Plesk,L=Schaffhausen,C=CH
* start date: Jun 19 20:27:17 2020 GMT
* expire date: Jun 19 20:27:17 2021 GMT
* common name: Plesk
* issuer: E=
[email protected],CN=Plesk,O=Plesk,L=Schaffhausen,C=CH
* NSS error -8181 (SEC_ERROR_EXPIRED_CERTIFICATE)
* Peer's Certificate has expired.
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
* Closing connection 0
curl: (60) Peer's Certificate has expired.
More details here:
curl - SSL CA Certificates
curl performs SSL certificate verification by default, using a "bundle"
of Certificate Authority (CA) public keys (CA certs). If the default
bundle file isn't adequate, you can specify an alternate file
using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
the -k (or --insecure) option.