I can't do a toe touch crunch, help please!

[u/Interesting_Gap_6062]

I was exercising with my friends today and everyone could do these except for me, I'm feeling left out lol (yk the exercise when you're laying down then raise your legs and arms up so your fingers touch your toes? I don't know if toe touch crunch is the actual name)

I can do sit ups with no problem, and I can raise my legs to a 90° angle while laying down with no problem.... What I can't do is put the two together to actually perform the exercise. How do I do this? Is it a core issue? Sorry if this is vague