Grizzly_UK wrote: »Problems like this is part of the reason I avoid using Steam for any MMO! Don't get me wrong, I have no problem with Steam itself, in fact I own 64 games on Steam, but none of them is an MMO. Don't know why but for some bizarre reason once Steam is involved players experience weird problems, usually in what is normally a simple and straightforward process!
I suspect the problem here is that the OP owns an older version of the game on Steam which is no longer available (as I recall Tamriel Unlimited is the version from back when the game went F2P) and has subsequently been "replaced" by the "Standard Edition" which includes the base game and Morrowind. So even though you're seeing "ESO" in your game library it's a different version than the currently available version.
When visiting the Steam Store page for ESO is the game shown with the "In library" flag to show that the game is already in your Steam library? I suspect it isn't because you own an old version that is no longer available to purchase on Steam.
When checking your actual ESO Account page what version of the game is displayed as owned? (Very first line on the right side, above "Account Status") This is the most important part because this is what determines just what you have access to in the actual game.
Which version of ESO do you want to buy? I only see two options for the game on the Steam Store ESO page:
Buy The Elder Scrolls Online Standard Edition (includes base game + the Morrowind chapter)
or
Buy The Elder Scrolls Online - Elsweyr (includes base game + Morrowind, Summerset and Elsweyr chapters)
What you see may be different in your country.
So what's the actual solution? Well I'm not 100% sure (some of the info in the links provided by VaranisArano is a little confusing) but so long as your Steam account is linked to your actual ESO account then whatever version(s) you buy on Steam *should* be added to your ESO account.