If it's not locked, not being worn, and is in the current characters inventory or bank then I would try re logging. The only other thing I could think of is if you just got it from a group dungeon and it's still on the trade timer, but I'm grasping at straws with that one.
Timers shouldn't be a problem. If it is on another character, you won't see them. You should be able to see them if it was in that character or in the bank and not locked.
Gan Xing - Crafting Nightblade Elrana Tinuviel - Hybrid Dragonknight
Elentári Peregrine - Sorcerer "bank" Rán Xīng - Hybrid Templar Laurïsil Imlachwen - Stamina Templar Helotë Tinuviel - Hybrid/Magicka Warden
Odin banker - obv banker
Yan of the Red Mountain - lvl 3 DK - not sure when I will work on em
@One_ofMany You'll probably want to make sure those aren't your starting items. I just double-checked (since I made a new character), and the items you get from the tutorial quests can be researched, but not deconstructed.
For example, Sentinel's Lash (and Heirloom Bow, if you have Morrowind) can be used to research the training trait on bows, but will not appear in your "Deconstruct" list.
As far as I know, the items that you may potentially have that cannot be deconned are:
Cadwell's Lost Robe
Er-Jaseen's Worn Jack
Heirloom Bow
Sentinel's Lash
Unfinished Torment Cuirass
Velothi Travel Guards