Hi Dloux,
welcome to the Apple (user-to-user) Community!
Re: Unable to create personal voice
Seems you need a Mac with Apple Silicon (ie: not Intel) to create a personal voice.
and you must also have a login password set.
(Also: Personal Voice may not be available in some languages).
Re: Apple Silicon: If in doubt, Apple Support provides this info. (from article below):
"To see whether your Mac has an Apple silicon chip,
choose Apple menu > About This Mac.
If a chip is listed — for example, Chip Apple M1 —
then your Mac has an Apple silicon chip."
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If all above is ok, and you haven't already:
Try restarting your Mac (ie: Apple menu > Restart)
(Deletes temporary files, re-establishes connections, may update recent setting changes, and often restores order if something is not working as expected.)
Then check to see if you can create the personal voice.
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If you still can't create the personal voice, and you haven't already:
With a browser open / accessible for the download:
You might want to try following the steps in Apple support's MacOS 15 article:
Create a Personal Voice on Mac - Apple Support
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If nothing above has helped: You may want contact Apple's Accessibility Support Team for help with the Personal Voice feature:
(ie: You can "Get Support" (online chat / phone / email etc.) from the "Get support" link at the bottom of their website:). Accessibility Support - Official Apple Support
All the best :-)