Hi kcgray632
welcome to the Apple (user-to-user) Community!
Re: "Siri responds with "uhm hum" to first request from locked screen"
Wondering if updating your iOS version to the latest one may help!
(NB: It is always wise to back-up your data first, if you choose to update.)
Apple support's online article: About iOS 18 Updates - Apple Support
says iOS 18.1 is the latest:
"This update introduces the first set of features powered by Apple Intelligence, the personal intelligence system that unlocks powerful new ways to communicate, work, and express yourself, all while protecting your data with an extraordinary step forward for privacy in AI."
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Else: If you haven't already: you could try restarting your iPhone: (ie: deletes temporary files, re-establishes connections, may update recent setting changes, and often restores order if something is not working as expected.) If needed: See how to: Restart your iPhone - Apple Support
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Trouble-shooting if needed: What to do: If Siri isn't working on your iPhone - Apple Support
All the best :-)