multiple email list not sending

I really like your contact form plugin and it really helps me a lot. Recently I tried to use multiple email address on the ’email to: box’ then I’ve notice it didn’t send out any email. I tried a couple of times still the same. I follow your procedure on the help but it is still the same. Right now I’ve set it to one email only because it is working perfectly on it. Thanks

Here is the form location: TLO

https://www.ads-software.com/plugins/si-contact-form/