"Thank you again!"
Ευχαριστώ πάλι sounds a bit weird. Ευχαριστώ και πάλι is what a native would say. (Και is emphatic here but required in this particular phrase)
I'm not sure if I'm far along enough yet but perhaps in the future could there be more sentences with the emphatic και? I read it a lot on online forums and it took me way too long to understand, haha.