SEE THE DIFFERENCE?

Luke 1:18

Zacharias and Elizabeth have been praying for a child. Both of them are old. One day, the angel Gabriel appeared to him and said that Elizabeth will bear a son.

Note what Zacharias answered.

And Zacharias said to the angel, "How shall I know this for certain? For I am an old man, and my wife is advanced in years."

Note what the angel said in verse 20.

"And behold, you shall be silent and unable to speak until the day when these things take place, because you did not believe my words, which shall be fulfulled in their proper time."

Luke 1:34

One day an angel appeared to a virgin called Mary and foretold that she will bear a child.

Note what Mary said.

And Mary said to the angel, "How can this be, since I am a virgin?'

Note what the angel said in v 37

"For nothing will be impossible with God."

Note the similar words of Zacharias and Mary.
Note the different response from the angel.

See the difference?