If this error occurs when you are on a Corporate VPN, where browser traffic is captured by a MITM (Man-In-The-Middle), you may need to change any or all of these settings in the Firefox
security.tls.hello_downgrade_check = false (this should definitely fix it)
security.tls.version.max = 3 (this should definitely fix it)
security.osclientcerts.autoload = true (this might fix it if it is OS cert-related)
The reason this may occur is because the security device is incapable of providing valid TLS 1.3 HELLO messaging.