webrtcsink works in GCP but not in AWS

Hi Folks

This simple test command:

gst-launch-1.0 webrtcsink name=ws congestion-control=homegrown meta="meta,name=test" videotestsrc ! queue ! videoconvert ! ws. audiotestsrc ! queue ! audioconvert ! ws.

works perfectly in Google Cloud:

gst-launch-1.0 webrtcsink name=ws congestion-control=homegrown meta="meta,name=test" videotestsrc ! queue ! videoconvert ! ws. audiotestsrc ! queue ! audioconvert ! ws.
Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Redistribute latency...
Redistribute latency...
** all good here, runs and streams**

but FAILS in Amazon Web Services:

gst-launch-1.0 webrtcsink name=ws congestion-control=homegrown meta="meta,name=test" videotestsrc ! queue ! videoconvert ! ws. audiotestsrc ! queue ! audioconvert ! ws. 
Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Redistribute latency...
Redistribute latency...
0:00:00.019017776  5932 0x7fc57c038c70 ERROR             webrtcsink net/webrtc/src/webrtcsink/imp.rs:3143:gstrswebrtc::webrtcsink::imp::BaseWebRTCSink::start_stream_discovery_if_needed::{{closure}}:<ws> Error running discovery: No caps found for stream video_0
ERROR: from element /GstPipeline:pipeline0/GstWebRTCSink:ws: There is no codec present that can handle the stream's type.
Additional debug info:
net/webrtc/src/webrtcsink/imp.rs(3144): gstrswebrtc::webrtcsink::imp::BaseWebRTCSink::start_stream_discovery_if_needed::{{closure}} (): /GstPipeline:pipeline0/GstWebRTCSink:ws:
Failed to look up output caps: No caps found for stream video_0
Execution ended after 0:00:00.004337575
Setting pipeline to NULL ...
Freeing pipeline ...

These were both built using the same installer, from clean Ubuntu 22.04 LTS images in the respective platforms. In both cases all external ports are open.

Could anyone explain what this means ?:

0:00:00.019017776  5932 0x7fc57c038c70 ERROR             webrtcsink net/webrtc/src/webrtcsink/imp.rs:3143:gstrswebrtc::webrtcsink::imp::BaseWebRTCSink::start_stream_discovery_if_needed::{{closure}}:<ws> Error running discovery: No caps found for stream video_0
ERROR: from element /GstPipeline:pipeline0/GstWebRTCSink:ws: There is no codec present that can handle the stream's type.
Additional debug info:
net/webrtc/src/webrtcsink/imp.rs(3144): gstrswebrtc::webrtcsink::imp::BaseWebRTCSink::start_stream_discovery_if_needed::{{closure}} (): /GstPipeline:pipeline0/GstWebRTCSink:ws:
Failed to look up output caps: No caps found for stream video_0

Many thanks !