Here it is pronounced more clearly. https://forvo.com/search/%d7%aa%d7%94%d7%a0%d7%94/ (hope that link works...if not, copy the word here and paste in the search thingy on the forvo site)
The difficulty is in translating בתיאבון, since it doesn't really exist in English (hence the French). תיאבון is appetite, loosely meaning "eat your meal with appetite", which is usually translated to "enjoy your meal". This is why the first "enjoy", תיהנה, can also be used in conjunction with בתיאבון. Does it make sense?
"Bon Appetit" is not English - very few Americans would use "bon appetit", even in restaurants (and very few Brits would either). They would say "enjoy your meal" or just "enjoy". It translates the same. Why give this answer extra complexity that is unneeded (and quite frankly, distracting - translating two languages)? (It says you can use "enjoy your meal" in the dropdown translation, but then tells me my response is incorrect when I put it in.)
The problem arises simply because although French has bon appetit and Hebrew and many other languages have an equivalent expression, there is no such expression in standard English. If you wish to say something, you merely choose whatever suitable words come into your head. In some circles it is not consider good manners to say anything of this nature and 'please start' is very often used instead.
I've haven't heard anything so silly in ten minutes. On what continent do you think this applies? Seriously. I've never EVER heard "please start." Good manners? is this a cult in Canada? or are you referring to people who don't speak English in the first place. That's not "some circles." You hear Bon appetit or Enjoy... or at a home dinner with non-family like at a potluck you might, might, hear dig-in (I've only read this or seen it on tv).
I've never heard "please start". I've heard lots of "enjoy your meal!" - which, again, is the equivalent. "Enjoy your meal" should be a perfectly acceptable answer in this case, but for whatever reason it is not. The reason requiring "bon appetit" is frustrating is that for many of us is that this is not a familiar word to spell. Meaning, I had to learn how to correctly spell "appetit" while also trying to learn Hebrew. Because I couldn't spell it, it meant my answer was marked incorrect even though I know בתיאבון . This complaint might seem silly to some people, maybe you, and that's wonderful that spelling isn't an issue for you. For some of us, spelling in English can be a struggle, let alone spelling in French. It is beyond ridiculous to not accept the perfectly acceptable response "enjoy your meal" which is both more common and the equivalent.
Anne, both you and TeribleTeri commented that you have never heard 'Please Start'. I thought of you today because my hostess said it at lunch. It is common here in the UK and considered to be good manners. The thinking behind it is that it used to be the custom to wait for the hostess to begin before guests would start. The current idea is for the hostess to tell the guests to begin especially when she might still be busy with serving etc. Perhaps not so silly after all!