DIAGNOSIS Yeah, this one's common. It's a connectivity problem. The device is online enough to hear you but can't reach Amazon's servers to process the request.
FIX First, check your Wi-Fi. In the Alexa app, go to your device and run a network diagnostic. More often, a simple reboot fixes it. Unplug the Echo Show 5 for 30 seconds and plug it back in. Let it fully boot up and reconnect.
IF THAT DIDN'T WORK The Wi-Fi radio in the device can get flaky. In the Alexa app, try forgetting your Wi-Fi network on the device and re-adding it. Sometimes it just needs to re-handshake with your router.
HEADS UP If you have a mesh network or dual-band router, try forcing it onto the 2.4GHz band. The Echo Show 5 can sometimes have issues hopping between bands automatically.