Acts 25:4

‘Howbeit Festus answered, that Paul was kept in charge at Caesarea, and that he himself was about to depart there shortly.'

We do not know whether Festus was a little suspicious about this request or not. He did, however, decline it. He pointed out that Paul was being held in Caesarea, and that he himself would be going there shortly. Even if he did not know about it, God did. Luke wants us to realise that God was still in control. Festus' reason might well have been that as a new arrival in the province he did not want to be away from Caesarea longer than was necessary in these first few days of his procuratorship. While the cat was away the mice could play. Or it may simply be that he resented being pushed around and wanted to establish his authority.