I’m unsure of your expectations - but consider the following...
iPad has Screen Mirroring - that reproduces what you can see on the iPad display - on an external TV or monitor. Screen Mirroring does exactly as its name implies; the iPad screen is reproduced on the external display, preserving the aspect ratio of the iPad screen.
AirPlay extends capabilities of iPad - permitting display of playing media content (either download or streamed) to an external TV or monitor, at full resolution and aspect ratio of the source material, independently of the iPad screen. This capability, however, does not extend to video conferencing Apps such as Zoom.
With these observations in mind, perhaps this support page will be helpful with troubleshooting the problem:
About Apple Digital AV Adapters for iPhone, iPad, and iPod touch - Apple Support