On your device: Settings > Privacy (or Apps) > Microphone, and make sure Trickster (or your browser, if you're playing via web) is allowed to use the mic. On desktop browsers, check the site's permissions via the padlock icon in the address bar.
Use your phone's voice recorder or a video call app (WhatsApp, FaceTime, etc.) to confirm the microphone itself works. This tells you whether it's a hardware issue or specific to Trickster.
If nothing else works, uninstall and reinstall Trickster. This resets any corrupted app-level audio settings that a normal restart won't fix.