If you can, set up your new Wi-Fi to match the last one the Express connected to (same SSID/network name and password). It should connect and then you can go back to using the app. There's also a method using multiple wireless devices with one acting as a hotspot configured to mimic your old Wi-Fi to set up the Express on the new Wi-Fi.
IR remotes rarely fail, but it does happen. I assume when you say it makes a sound you're referring to the sound coming from the TV and not the remote itself.
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