audio mixdown problems, only 1 track?

Just started using Cubase for the first time in a very long time and I’ve been having issues I never had before. Whenever I export a file as an mp3 it only gives me the first track in the song, but when I use any other format it gives me the full song. This is problematic because I need to send it to people and I keep running into size limits with .wav files. I recorded on a Scarlett 2i2 if that helps, and my PC specs are in my sig.