Why cant i make this stereo?

You have placed the stereo clip on a Mono track, thats why. Use Stereo tracks or Standard tracks.

And, you have a sequence with the Mix set to 4 tracks, so may probably just need a sequence with the Mix set to Stereo. You cannot change that, you must create a new sequence but you can easily copy track from another sequence to the new one. If you want/need to keep the 4 track Mix sequence, don´t forget to pan Left to Left and Right to Right to get proper stereo playback.