One thing I see is that you are using port 8999, The ONVIF port for the camera is 80.
Here is what pops up with my find/inspect for this camera:
Opening 192.168.1.108 port 80...
HTTP Get / request...
OK
ONVIF GetSystemDateAndTime
2022-10-23T17:12:20.000Z
Requesting device information...
Manufacturer: Dahua
Model: DH-
SD49425XB-HNR
FirmwareVersion: 2.800.1341000.0.R, Build Date 2020-03-12
GetCapabilities...
Querying services
Has Search services: /onvif/search_service
Has Imaging services: /onvif/imaging_service
Has media services: /onvif/media_service
Has RTP_RTSP_TCP, requesting profiles
profile token MediaProfile000
profile name MediaProfile_Channel1_MainStream
profile source is 000
profile source config is 000
profile token MediaProfile001
profile name MediaProfile_Channel1_SubStream1
profile source is 000
profile source config is 000
profile token MediaProfile002
profile name MediaProfile_Channel1_SubStream2
profile source is 000
profile source config is 000
requesting URI for profile MediaProfile000
RTSP URI: /cam/realmonitor?channel=1&subtype=0&unicast=true&proto=Onvif
requesting URI for profile MediaProfile001
RTSP URI: /cam/realmonitor?channel=1&subtype=1&unicast=true&proto=Onvif
requesting URI for profile MediaProfile002
RTSP URI: /cam/realmonitor?channel=1&subtype=2&unicast=true&proto=Onvif
Has Event services: /onvif/event_service
Has WSPullPointSupport
RelayOutputs: 1
RelayOutput: 000/Bistable/open
InputConnectors: 2
Has Device IO services: /onvif/deviceIO_service
AudioOutputs: 1
Has PTZ service: /onvif/ptz_service
Preset: 1=Startup
Preset: 2=DWWide
Preset: 3=DWNight
Preset: 4=Vehicle
Preset: 5=FrontDoor
Preset: 6=Sidehouse
Preset: 7=Mailbox
Preset: 8=Upstreet
Preset: 9=DownStreet
Preset: 10=Downstreet2
Preset: 11=LPRupstreet
Preset: 12=Weather
Preset: 13=2AM
Preset: 14=DownSpotter
Preset: 15=UpSpotter
Preset: 16=DownSpotterDay
Preset: 17=DownSpotterNight
Preset: 18=DownSpotterNightNew
Preset: 19=DownSpotterNightZone
Done