The short answer
Audio must exist in the source profile and be supported through the playback path. Hearing sound is not proof of two-way talk support.
Work through the checks
Use ONVIF-reported media profiles where available, and record the selected profile token. Profiles can differ in resolution, codec, audio and PTZ associations.
Read the codec for the selected camera profile rather than inferring it from resolution or filename. Test a documented baseline stream without changing every encoding option at once.
Check whether the selected profile actually carries audio and which audio codec it uses. Compare a known audio-capable source before treating silence as a speaker or volume problem.
Compare the failing source with a known working local source using the same computer. Keep credentials private and use your own authorized devices; do not test unknown public camera feeds.
What to verify
When the issue remains, send support the app version, camera model, firmware, error time and a redacted connection format. Include what changed between a successful and failed test.
Sources and scope
AeoCam is available for Windows. Camera settings below describe protocol preparation, not a certification of a particular camera or a promise of every feature in every app version. Check the installed build and the Microsoft Store listing for current availability.
Vendor documents describe the camera or protocol. No physical-camera compatibility test is claimed here. Menus and capabilities can change with model and firmware.