Hello@Stonie 

Tapo Camera use G.711 for  audio commanding and the player support playing G.711 encoded audio files.

Please refer to 'What if the recorded videos have no sound?' for more details:  https://www.tp-link.com/support/faq/2905/

May I know which player you have been using, can you hear sound on TC60 and a C100 using the same player when do rtsp streaming? What is the software version of the Player?

Hello@Stonie, 

The codec supported by tapo camera should be the same. 

May I have a link of the surveillance software you are currently using, please make sure its firmware is up-to-date. 

Can I have a photo showing the Audio option when you try to stream on Tapo C310 & a  photo of streaming the TC60/C100. 

@Stonie Thanks so much for sharing all the detailed info! As this issue  sounds unusual, we would like to have a specialist look into this further through, please check your mailbox later. To expedite the problem resolving  it is also suggested to contact NUUO NVR support side and see if they have any suggestions, feel free to let us know how it goes, thank you

Hi @Stonie 

I escalated your case through email with forum ID 503310， did you receive the email, feel free to let me know if there is any update for this concern, thank you.