Welcome to the forum, Kevin.
You have latex or siliconized-latex caulk in the corner. There's been too much movement for the caulk to handle. The more proper material would be a sealant like 100% silicone that has much more flexible properties to it. If you want to clean that out, you can remove it carefully with a razor scraper (be careful not to scratch) or a relatively sharp plastic putty knife that you keep sharpening as it dulls. Then apply the silicone.
If you can't find a good color of 100% silicone locally, you can buy any color 100% silicone you'd like from
ColorRite (product is called Color Sil). It's a little pricey. You'll probably spend $25 for a tube with shipping. But having a color matched silicone allows it to blend in with the rest of the installation well.
And if using silicone makes you nervous, just holler and we'll walk you through how to do a neat job. The same folks at ColorRite also sell a "Mist" spray and a "Perfect Bead" tool to make forming a neat bead relatively easy. It takes a little practice, but it's not hard.
