Anything showing towards the top of your screen under My Account > Passes & Vouchers page such has " Vouchers Waiting For You" with a link ?
Also go into the NowTV stick App and under the My Account section to see if there is any active passes ready to start and double check the email address or username that you setup the stick on, just in case it's different to the one you are trying to locate your passes on here.
Jump over to live chat to see if they can figure out where your missing vouchers are that came bundled with the stick.
Live chat might ask you to factory reset the stick to see if the voucher passes then somehow appears on your account (though let live chat instruct you accordingly on what actions to follow).
Do you need a link for live chat ?