I'm unable to use the grenade or mines. I've selected them in the PIPboy but they never appear for me to use, it's pretty frustrating when I'm facing 4 or 5 bad guys and I can't blow them up!

They don't appear or equip in your hand like they previously did. You still hold your equipped weapon like normal. Hold down R1 and you'll hear a click basically telling you the grenade or mine is activated and then release and it should throw.