Hi,
In order to put the reviews into a tab, you have to move the tabs outside the product form.
Because the reviews use a form too and you can't put a form in to a form, you have to keep them separated.
It is the main thing I know which can block the reviews into a tab.
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.