Disappearing Siri voices for VoiceOver and Spoken Content
There is a bug that Apple hasn't been able to fix. Ever since the first iOS 13.0 release, Siri (male or female) will work with VoiceOver and Spoken Content services for a while but eventually crashes. Once Siri's voice crashes, Spoken Content features stop working; VoiceOver at least has the decency to fallback to Samantha. Siri voices will then appear on the list as if they aren't downloaded. Sometimes you can even redownload them and have the working again for a little bit, but they'll eventually crash and stop working again.
Unfortunately the only way I have been able to solve this problem and have Siri voices working all the time with VoiceOver and Spoken Content, is by factory resetting my iPhone and iPad and setting them up as New devices. The moment I restore from a backup, whatever is causing Siri to crash gets restored as well. Something when restoring backups or transferring settings from another devices is what is causing this problem that has plagued us for many, many months.