Air carrier Captain reported receiving a warning message after releasing the parking brake for not accepting the loaded dangerous goods. After the DG was secured; the flight departed.

Narrative

There are two Dangerous Goods (DG) incidents that occurred on this flight. First; I was not made aware that any DG was planned or loaded on the aircraft until I released the parking brake and received a warning message that I had not accepted the loaded DG on my airplane with the dangerous goods acknowledgment code. I immediately set the parking brake and queried the ramp crew if any DG had been loaded. They informed me that there in fact was DG; Radioactive Yellow II; that was loaded on the airplane. I stated that I never received a Final DG Summary and knew nothing about it. About 7 minutes later the Final DG Summary printed in the cockpit and I accepted it by sending the dangerous goods acknowledgment code. I then received acknowledgement that my acceptance was received.I then asked the ramp what else was in the cargo hold and was informed that they loaded a wheelchair with a lithium-ion battery. I did not receive any paperwork for that either and told them that I needed the Battery Powered Wheelchair or Mobility Device Tag. They got me the tag a few minutes later but it was not completely filled out. I then contacted the Chief Pilot to make sure I handled this properly and he gave me the phone number for the Dangerous Goods department. I called them and ran the scenario by them to make sure the ramp crew properly loaded the wheelchair and subsequently secured the battery correctly. After verifying with the ramp crew that the battery was correctly secured and which method had been used to secure it; I proceeded with no other issues.