Northwood factory sealant/Sikaflex useable shelf life

I am having a hard time trying to understand how you have such a large gap. Do you have to cut material to fill that gap or can you just fill it with sealant? It looks like it needs more than sealant but I cannot tell how deep the gap is or what is behind it.

Anyway it does seem that you came out lucky on this and only have some repair work without any major damage aside from the initial poor construction.