Ok here is an update for me. I'm not trying to refute people having key problems or missing content or missing keys which I do believe others are having problems with.
Quick Version:
Season pass is working in the game for me even though uplay has no green check mark for dlc and the in-game menu always says "get season pass now"; which is why I was concerned.
Basically, for my Far Cry 4 Gold Edition which I got from steam and inserted both the Far Cry 4 key and Season Pass key into uplay, I found the Day 1 season pass mission "The Syringe" later on even though I have no green check mark for DLC for Far Cry 4 in uplay and also the in-game menu always says "get season pass now".
If you want details read more.
Long Version:
The day 1 season pass mission "The Syringe" finally did appear on the map for me. As far as I know that is all that the season pass gives as of this moment.
This unlocks further into the game. For me it finally showed on the map after I beat an assassination mission at the Kyra Tea Terraces. But it might be because my in-game Karma level got high enough also, not sure.
Here is a picture of where the assassination mission was located to start it. Since I done the mission already, you wont see it in this picture but that is where it was located. (Where the game's mouse pointer is.)
http://cloud-4.steampowered.com/ugc/...398D57CEE75B2/
If you don't see the assassination mission, then you might have to do enough story for it to finally appear, I guess. You might have to clear the fog on the map in these areas in order to see this mission or to give missions the ability to appear later on. But having the fog cleared didn't make "The Syringe" Mission appear in itself. You clear fog from the map by taking over the radios at the top of the bell towers throughout the map.
After I beat it, the syringe mission popped up finally on the map.
http://cloud-4.steampowered.com/ugc/...8BB481F9CF352/
Again, I bought the steam's pre-order far cry 4 gold edition, inserted both keys into uplay and do see the keys are in my "account information" for uplay (after clicking the gear symbol at the top of uplay in the upper right). Also there is no green checkmark for me at all in the dlc section for the game in uplay and also the game does always say "get season pass now" for me. So it seems as long as the keys are located in the account information then the season pass is active in-game. At least in my case.
The Butchers Machete, Driller PKM, Elephant Gun .700 Nitro, Sandman 1911 Pistol, Hurk's Return mission, and Blood Ruby mission, all seem to be the bonus stuff from the pre-order of far cry 4 itself, not from the season pass as far as I can tell since all these things are tied to the same serial key for far cry 4, and not to my season pass key as I look in my uplay's account information.
At the beginning I did get the Elephant Gun, Driller, and Sandman weapons at the first armory in the Signatures section. I think the other weapons you will get after you beat the Hurk's Return mission and Bloody Ruby mission which I haven't done yet. So if you don't see at least those 3 weapons there then it does be that you are missing the free content from the pre-order, at least from the pre-order Far Cry 4 gold edition from steam. I would think though the same content would be also from the uplay's pre-order.
For the Steam Gold Edition, I noticed that in steam, the DLC tab for the Far Cry 4's games properties didn't have everything installed. Both "Far Cry 4 Gold (ROW) - Uplay Activation" and "Far Cry 4 Season Pass - Uplay Activation" were installed but "Far Cry 4 Season Pass" wasn't so I made sure to check the box. Still though after doing this I still get no green check mark for the game's dlc in uplay and still always get the "get season pass now" message in the game itself but it appears all the content is in the game, at least in my case.