Pitch shifted after reloading project


I’m currently working on a song and everything has been fine so far until i loaded my project today and noticed something was different.
I compared it to my audio mixdown of yesterday and noticed the project is suddenly transposed a whole step up and i have no idea why and how i can fix it so it is back to original pitch.
I’m kinda new to Cubase and its features so i thought i might get some help here.
I’m using Cubase LE8 on Windows 10 with a Focusrite Scarlett 2i4 audio interface if that information is relevant.

Maje sure the project- audio- and soundcrad samplerates match

It was actually the samplerate. Now everything is fixed, thanks!