Speak commands produce no sound on Safari 14.0

[amyjko]

Expected Behavior

Programs with a speak command, when run, should produce audible, synthesized speech.

Actual Behavior

No speech is generated.

Steps to Reproduce

• Open Safari 14.0 on macOS 10.15.7
• Download this file: https://drive.google.com/file/d/1FWkWq86w_GsQjcemWTZhR_EFzLq6Sm00/view?usp=sharing
• Open the file at https://codelab.cognimates.me
• Attach "speak hello" to the when clicked event handler
• No sound is produced
• An error appears on the console that says something to the effect of "Feature not supported", with a mention of the synthesizer.

Unfortunately, after reloading, the above steps do not produce the failure, so I'm able to reproduce this again to obtain the precise error. It may be intermittent.

Operating System and Browser

e.g. Mac OS 10.11.6 Safari 10.0