How can I get Post Processing to show in the viewport AND in my camera pointed at my rendertexture? (separate from my fps main camera)

I'm a beginner at Unity but I've set up my simple scene and want to apply post-processing on top of my camera.

I am using a render-texture and a camera pointed at it to render my game in a PS1 style, if I attach my post processing to my FPS camera I can see it in the viewport but can't see it in the game. I assumed this was because my render texture was rendering the view from the FPS camera without the PP on it for some reason. I've tried to fix it by changing the colour profile (I read in another post that it could be to do with colour format but changing those settings in the render texture doesn't actually do anything).

The thing is, if I attach my PP volume to the camera pointed at the RT then the bloom (the specific PP effect I'm looking for) works in game but then doesn't work in the viewport. I'd like it to work in both the game and the viewport but I'm not sure what else to try.

Any help would be much appreciated! Thanks!