Are you setting IdNNTP1.UseTLS to utUseImplicitTLS when using port 563? On port 563, an NNTP server requires the client to complete a successful TLS handshake before the server can then issue the NNTP greeting.
Note that modern usage of TLS for NNTP discourages the use of port 563, instead preferring the 'STARTTLS' command on port 119 instead, which delays the TLS handshake until the client explicitly requests permission to initiate the handshake after validating that the server even supports TLS.
Do you have the same problem if you set IdNNTP1.Port to 119 and set IdNNTP1.UseTLS to utUseExplicitTLS?
Note that modern usage of TLS for NNTP discourages the use of port 563, instead preferring the 'STARTTLS' command on port 119 instead, which delays the TLS handshake until the client explicitly requests permission to initiate the handshake after validating that the server even supports TLS.
Do you have the same problem if you set IdNNTP1.Port to 119 and set IdNNTP1.UseTLS to utUseExplicitTLS?