Thanks for reaching out and sorry to hear that you're having trouble in using XD. I'd request if you can share a few more details like:
The version of XD.
The version of Mac or Win which you are using.
If it is happening with a specific file or multiple files, will it be possible for you to share the file with us?
Is it possible to share a video of your workflow which you are working on so it will be useful to reproduce the issue from our end. Tried to reproduce your issue from our end on latest XD version-18.104.22.168 on Mac machine, but voice command feature in prototype is working fine without any Issue, so please share the above mentioned details.