Melissa has too many potential pronunciations

Here are two, in IPA (https://en.wiktionary.org/wiki/Appendix:English_pronunciation):

/məˈlɪsə/
/meɪlisɑ/

Consider something that's a little more internationally pronounceable in order to avoid having multiple names for your product across the globe as you expand.

Definitely don't exceed three syllables, but two is probable a goal. "Siri" is two, "OK, Glass" is three, and "OK, Google" is four. You know what's easier to say quickly!