Unable to connect. Check your internet connection and try again.

OK, this is very bad and something you folks should fix yesterday.

The error appears only if the text to be turned to audio contains SSML tags.

My guess is now: at least one SSML tag is invalid or unsupported, and also Storyline gives a useless and incorrect error message when that happens. I'm attaching the text (none of it is a trade secret or anything) including tags, in case that will help with debugging.

As a former software dev and also software designer and product manager, let me further say: error messages should help the end-user. If there's (for instance, totally randomly selected) an unsupported SSML tag, the correct error message would be

 "SSML tag incorrect or not supported by Storyline: " + $SSMLTAG.

 

This text gives the error.

<speak><emphasis>test</emphasis> test test</speak>

The <emphasis> tag is explicitly supported by Amazon Polly. I have zero idea what's up here.

Confirm the incorrect error with invalid SSML: if I typo "+6dB" as "+6db" the capitalization error gives the "Unable to connect" message. 

Also, I'm using a neural voice. I remember changing it, but apparently it got switched back at some point. OK, neural voices don't support <emphasis>, but surely you could say "The <emphasis> tag can only be used with standard voices" instead of what now happens. In any case, I just used the +6dB option (of the <prosody> tag) instead. Maybe Articulate could preempt Amazon and automatically replace <emphasis> when using a neural voice, saving us end-users some effort?