Air carrier flight crew reported gate pushback without DG Summary and without sending the DG acknowledgement code. The flight waited until required documents were received and acknowledged before taxiing for departure.

Narrative

When we initialized the aircraft we received a no dangerous goods message. Upon push back the First Officer informed me that we received a pilot notification warning message saying that I must acknowledge receipt of the final pilot notification message. Since we were already being pushed back I elected to continue the push back instead of trying to stop it and potentially cause some safety issues. After push back I contacted operations and told them about the pilot notification message and that we had received a no dangerous goods message prior to push back. They told me that there was some dangerous goods but not the type and quantity that were needed to generate a final dangerous goods summary. He said he was still checking into it and I told him that we weren't going to taxi until we had the issue resolved. After about 5 minutes he told me that there was dangerous goods on the plane that required a final dangerous goods summary. He sent it to us and we received the print out of the final dangerous goods summary. We then sent the ACARS dangerous good acknowledgment and the situation was resolved. I then commenced the taxi phase.