PDF generate from our web server behind firewall alwasy blocked

Do you run the firewall and do you have access to the logs? Have you looked for any logs of why this is being blocked? Are you running Intercept X that could also be blocking the PDF locally? Do other PDFs come through reliably?

Do you have advanced protection enabled? It will flag PDFs, in particular short ones, to send off for Sandstorm "detention" which would normally allow the PDF through if it passes, but if the PDF (name) and contents are dynamic it may never be able to say, "This has been examined and is fine" because it's a different file every time. I believe you can add exceptions to Sandstorm.

Do you run the firewall and do you have access to the logs? Have you looked for any logs of why this is being blocked? Are you running Intercept X that could also be blocking the PDF locally? Do other PDFs come through reliably?

Do you have advanced protection enabled? It will flag PDFs, in particular short ones, to send off for Sandstorm "detention" which would normally allow the PDF through if it passes, but if the PDF (name) and contents are dynamic it may never be able to say, "This has been examined and is fine" because it's a different file every time. I believe you can add exceptions to Sandstorm.