Matthew 16:1-4 (ESV)
And the Pharisees and Sadducees came, and to test him they asked him to show them a sign from heaven.  He answered them, "When it is evening, you say, 'It will be fair weather, for the sky is red.'  And in the morning, 'It will be stormy today, for the sky is red and threatening.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times.  An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of Jonah." So he left them and departed.
It is peculiar, Jesus gave all sorts of signs, but the Pharisees wanted their own, like Gideon they were not content with the signs already given, but would test the lord in their own way. Jesus had given them the signs they needed. But these were not good enough for them.
In reality it is a desire to control Jesus that makes them ask for a sign. Jesus knew what they wanted. In short they did not want to believe in something they could not control. They were unwilling to believe in jesus based on what he had already done.
It is an Evil and adulterous generation that seeks a sign. The same is true today. Jesus has done enough to show us who he is if you just investigate the texts testifying to him, but people won’t. They want something more. They want to have a burning bosom, or to speak in tongues, or a miraculous transfer of funds into their bank account. Jesus doesn’t work that way. He gives us what we need. If we don’t want to believe that is our problem.