Become a multi-million dollar dealer/installer of their gear LOL.
Otherwise what you experienced reaching out to Dahua is exactly what we would expect because we simply are not their target audience, it is the professional installers/distributors that are authorized to sell and install this gear, so we cannot purchase directly and thus they will not take your phone call for support related questions or suggestions -
they will tell you to talk to the installer/distributor you purchased from for sales, support or firmware updates.
Many people have bought a "Hikvision" or "Dahua" from Amazon or some shady foreign website or a 3rd party seller or even an authorized distributor and when they call Hikvision or Dahua for support they basically tell them to go pound salt - we have dozens of threads were people come here after trying that route. We simply are not their intended market to sell to and they will not take your call for support...Lot's of threads here confirming this, including one from a few
months ago where someone tried to call for support and they told them sorry talk to their installer.
And now we can add your post to the growing list...