PROBLEM: According to Jesus’ statement here, He would not always be with the disciples, for He said: “but Me you do not have always” with you. On the other hand, in Matthew 28:20 Jesus said, “Lo, I am with you always, even to the end of the age.”
SOLUTION: In the first passage, Jesus was speaking of His physical presence (which would not be with them between His ascension and second coming), and, in the later text, He is referring to His spiritual presence with them as they preached the Gospel in all the world. There is no contradiction here whatsoever.
Geisler, N. L., & Howe, T. A. (1992). When critics ask : A popular handbook on Bible difficulties (359). Wheaton, Ill.: Victor Books.