How do I talk to Sinding?

When I went into the jail, I saw Sinding in one of the cells, but he's very far away so I can't actually talk to him, and I can't open the door to the cell (if it is a door).

How do I talk to him? I am playing on the PS4.

Solution 1:

If I remember correctly, it might take a while for him to approach the cell door.

You can also try reloading an earlier saved game, and reentering the Falkreath Barracks.
Apparently this is also a method to fix a known bug:

Sinding may get stuck on the stairs in his Falkreath jail cell, which can prevent him from getting close enough to the bars to talk to you, thus preventing the quest from progressing.