Solved it just now. It took a call to Apple, and I wanted to share the not-obvious-to-me solution. Something inside my longstanding Admin account was blocking the required Voice Command package download from completing successfully. Nuking and re-creating my Admin account seems to have fully resolved the issue.
Cheers! Stay safe and healthy...now with Accessible Social Distancing!
=== informal notes ===
Same problem here. Trying out Advanced Dictation for the first time...huh! Replaced by Voice Control with Catalina.
OK, no troubles. Enable Voice Control > the checkbox in system preferences spontaneously unchecks after a few seconds. Same message as quoted above logged in /var/log/system.log:
Apr 4 11:40:56 <My>-MacBook-Pro assistantd[2118]: rootless_convert_to_datavault: rootless_set_storage_class(/Users/<myuser>/Library/Caches/VoiceTrigger/SATUpload): Operation not permitted
I added user+group+other Write permission to this folder. No luck.
Removed (renamed) ~/Library/Caches, so whatever cache is the problem would start fresh. ALSO no luck.
Rebooted in Safe Mode. (I'm not sure how this would help...whatever Safe Mode is, it also didn't help.)
Called Apple Support. Their wait times are REALLY LONG right now. (Like 45 minutes. There are a HUGE number of people who are trying to work from home...including a TON of MDs seeing patients with a telemedicine visit for the first time ever. I get it! Thanks Apple for providing and supporting this life-saving technology!!) I persisted on hold and got a helpful human tech.
Here's the steps which worked for my 2016-vintage MacBook Pro:
- Preferences > Users > Create new Admin account
- Log in as the new Admin account.
- Preferences > Users > Delete the existing Admin account. (!!! BE SURE TO not change the Home folder. This was all of my user data. Back up your mac if you have not done that recently!!!)
- Preferences > Accessibility > enable Voice Control. (The microphone widget appeared for the first time ever!)
- Finder > browse to /Users, find the folder for <mylogin>, which is now called "<mylogin> (Deleted)". Rename to "<mylogin>".
- Create new Admin user with my original identity. Choose "reuse existing home folder", and make that account an admin account.
- Log in as my original identity.
- Delete the temporary Admin account.