I HAVE NOT SEEN YOU ,

I HAVE NOT SEEN YOU ,
I HAVE NOT SEEN YOU ,

I HAVE NOT SEEN YOU ,
语法没问题.

对啊!i haven't seen you for ages!

I HAVE NOT SEEN YOU
一般不单独使用，如果加上
for years 更好
i have not seen you for years
好几年没见了。

语法没问题，如果后面再有个时间限制就更完美了，但不能全部都是大写的啊