Show an image with a mask and border color at the bottom

There's several ways I can think of to do this:

• Use a Beam effect and keyframe its transition down the image to match the timing (you could use a linear expression for this if you feel like a challenge)
• Use another layer for the green border and a Linear Wipe transition effect.  I'd be tempted to use an expression for this as you can have it match the transition with a +5% - which means it would automatically be replaced at the end of the transition.
• Use a Layer Style's Stroke on the image to add the border and keyframe its opacity and thicknes

Make sure you only have one mask. It would be nice if you upload a screenshot of the whole interface to try to see more than just that bit of composition. A precomposition would also be a possible solution.

Hi there 🙂
Is it possible that your image has a drop shadow (layer style or effect)? Or did you import it as PSD and put a drop shadow behind it? AE will keep the layer style. If that is the case, you could try to hide the effect and see if the border still appears. If it's still there try to precompose the image and then apply the mask to it.