Relevant passages:

Genesis 32:30
And Jacob called the name of the place Peniel: “For I have seen God face to face, and my life is preserved.”
Exodus 33:11
So the LORD spoke to Moses face to face, as a man speaks to his friend. And he would return to the camp, but his servant Joshua the son of Nun, a young man, did not depart from the tabernacle.
Exodus 33:20
But He said, “You cannot see My face; for no man shall see Me, and live.”
John 1:18
No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him.
1 John 4:12
No one has seen God at any time. If we love one another, God abides in us, and His love has been perfected in us.

At first, one might think this is among the greatest of alleged contradictions, for its form mimics the Law of Non-contradiction. A contradictionist may say, “We’ve got a good one on you because A cannot equal not-A, and these verses show that God can both be seen face to face and not.” But sometimes people fail to realize the rest of the Law of Non-contradiction that states, “A cannot equal not-A at the same time and in the same relationship.”

Usually, when I see two verses allegedly in contradiction so close together in context, e.g. Exodus 33:11 and Exodus 33:20, then the context will be significant in helping us reveal there is a different time or relationship, hence not in contradiction. And this is exactly the case here. Between Exodus 33:11 and Exodus 33:20, Moses and the Lord are speaking, but a change in relationship occurs in verses 18 and 19. The greater context of this is shown:

17 So the LORD said to Moses, “I will also do this thing that you have spoken; for you have found grace in My sight, and I know you by name.”
18 And he said, “Please, show me Your glory.”
19 Then He said, “I will make all My goodness pass before you, and I will proclaim the name of the LORD before you. I will be gracious to whom I will be gracious, and I will have compassion on whom I will have compassion.”
20 But He said, “You cannot see My face; for no man shall see Me, and live.”

At this point, the relationship has changed to signify that Moses asked to see the Lord in His glory! Not the typical face to face as revealed to sinful humans and as had already been revealed to Moses. Then, the Lord informed Moses that if any man saw Him face to face (in His glory), then they would die (see also 1 Corinthians 1:29).

The context of John 1 reveals a similar situation of God in His glory:

15 John bore witness of Him and cried out, saying, “This was He of whom I said, ‘He who comes after me is preferred before me, for He was before me.’”
16 And of His fullness we have all received, and grace for grace.
17 For the law was given through Moses, but grace and truth came through Jesus Christ.
18 No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him.

John discusses God’s fullness (hence, His glory) in verse 16 and points out that no one has seen God (in this fullness), but Christ, who declares Him (who was God in humbled flesh, according to Philippians 2:8 and the earlier context of John 1). The verse in 1 John 4:12 restates John’s previous statement and is, thus, not in contradiction, but consistent as well.

Hence, there is no contradiction, as God can speak face to face with men, but not while in all His glory; otherwise, sinful man would die.