URP Particle Texture Sheet Animation Texture Not Avaialble

I'm trying to apply a Texture Sheet Animation effect to some particles created in URP. I've got the particles working with the texture applied, but they are showing up with the full sheet being emitted from the emitter. Obviously, the next step is to apply the Texture Sheet Animation module to the particle system and set the sampling and timing modes, but for a reason I don't understand, the sheet isn't showing up in the selector to designate the texture and I can't find a way to make it accessible. Only the default textures are showing up, and I can't find how to make the imported sheet accessible to the module.

I'm using Unity 2021.2.411, and I have been able to make other textures available to the Texture Sheet Animation module, so this is odd. Any specific info that I'm not finding, such as a specific folder or naming convention I need to follow, would be much appreciated!