I am unable to install new voice packages on my system. I have reviewed some similar questions to this, such as this one. But I have not been able to find any recent information on this issue.
There are two related places of concern:
Settings > Time & language > Speech
Under Manage Voices, the Add voices option does not work. Specifically, when I select a new voice there from the list, a message displays instructing me to reopen Settings for the changes to take effect, however nothing actually changes, and no package is installed.
Settings > Time & language > Language & region
Next, I tried adding languages here via the Add a language button. This time, language downloads began, but failed mid-way.
Following this, returning to Settings > Time & language > Speech now displays entries for the languages that failed to install on the Language & region screen, however they show a size of 0 MB and I am unable to remove them, and their voices are not available:

(Curiously, my original system language of "English (United States) also shows a zero size; I'm not sure if that's atypical.)
Thank you in advance for any help you might provide.