Piri is pearOS's Siri-style voice assistant. Its speech model is a few hundred MB, so it's deliberately not downloaded during install/first-boot setup - it's fetched the first time you actually log into your real account, from cdn.pearos.xyz.
If Piri isn't responding yet, it's most likely still downloading (or failed to, silently, if you were offline on that first real login). Check whether the model actually landed:
ls /usr/share/extras/piri/model
If that's empty, connect to the internet and log out/back in once to retrigger the download, or open System Settings → Piri and try enabling it again from there.