Is there a layer selection? I did all the text before putting in a background video, if that helps.
Using: Hitfilm Express Starter.
try making it a composite shot
I think then you can access the layers
Normally, you add the video, then add the text, the text can be on video 2 or 3 with your primary video on video 1, that is your base layer, any B roll for instance typically goes on video 2, with the top layer being video 3 would be your text, so that should be your top layer in other words. You can do more then 3 layers, but that is an example of how to do this.
So in the future, your base video should be on the bottom and each layer lays on top of, with the top layer being your final layer, in your case, the text, which can also be video 2, as long as it's on TOP of your video as it's being keyed on top of.
Composite will work, but I think the same rules apply here as well, with the differences being you can do special effects or key frames and what not as well, which is needed for some effects.
Hope this makes sense.
@littlehausbigcity did a pretty good explanation, but here's another.
Consider this image.
This is a traditional cel animation setup. The background plate is a full screen painted image while Bugs Bunny is drawn and painted on transparent acetate, which is placed over the background then photographed.
This is kind of how all NLEs order images.
An Editor and Composite Shot are calculated and rendered from the BOTTOM layer UP. Whatever image is on top covers images below.
Now, each clip, whether on the Editor or in a Composite Shot will have a set of Controls in a Controls panel like this.
Everything in the Controls Panel applies from the TOP moving DOWN. So Masks apply before Effects, and an Effect at the TOP of an effect stack applies before an effect at the BOTTOM.
Knowing this order of operations - layers and tracks apply from bottom up, tweaks withing a clip from top to bottom - will help you plan out your shots.