Hi,
It depends on what you call an invoice.
The vendors receive order notification like your admin receive the store order notification.
If you want to check that your vendors right receive it, you have to add a user in their vendor account and gave him the "order / notification" right ; so it will be notify by email for the orders.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.