All of my sea of thieves progress has been lost, how do I get it back?

I have recently tried to play sea of thieves through steam after resetting my computer. To my surprise, when I logged in with the email that I have always used - the game prompted me to choose a new gamer tag and pirate, with no indication as to where all my progress was. I tried to choose my initial gamer tag (which I had all the progress on) “” but I was told that the name was not available. I then choose the gamer tag “Tigertoob” however the game then proceeded to treat me like a new pirate with no knowledge of my past progress.

On steam it still displays my 400 hour play time and achievements that I have made along the way. As well as the twitch drops and other rewards I have collected whilst playing the game.

I love the game and the experiences that I have had on it and have never done anything malicious or offensive towards anyone online.

If anyone could help me in the right direction to getting all my progress back, I would be deeply grateful.

:)