"At that time if anyone says to you, ‘Look, here is the Messiah!’ or, ‘There he is!’ do not believe it. For false messiahs and false prophets will appear and perform great signs and wonders to deceive, if possible, even the elect. See, I have told you ahead of time.
So if anyone tells you, ‘There he is, out in the wilderness,’ do not go out; or, ‘Here he is, in the inner rooms,’ do not believe it". Matthew 24:23-26
The confusing thing in the passage above is that Jesus is telling us not to believe when someone comes with signs and wonders claiming to be the Son of God.
How then will we know? How can we be sure?
Jesus performed many miracles but there were still people who didn't believe him
In a world filled with so much deception it's hard to believe anything
The coming of the lawless one will be in accordance with how Satan works. He will use all sorts of displays of power through signs and wonders that serve the lie. 2 Thessalonians 2:9
The evil one is quite capable of performing signs and wonders. He masquerades as an angel of light. 2 Corinthians 11:13
It will be very hard to know for sure if the person claiming to be the Son of God really is.
Many people believe that the age of apostleship ended after St Paul and reject any prophet and/or revelations which occur after it.
This view makes it impossible to accept Christ when he returns