Try see here:
Sindings page mentions him appearing in several places including the cell but thats after the quest.
To start the quest you can talk to Mathies instead of going right to Sinding you might still be stuck if the werewolf version is still in the cell (but it might be worth a try). If your on a PC and can start the quest with Mathis but it still gets stuck you could try console commands not sure how well it would work though.
u have try TCL (make sure do no have value of any object previw clicked, or dont click in any);
Am I suppose to be able to speak with Sinding when he sits in jail? Cause I have no clue what I'm are suppose to do now. The quest now only tells me to go and speak with Sinding and that he is in jail. But I cant speak with him cause he does not say anything and are now stuck. Someone who might be able to help me?
To start the quest you can talk to Mathies instead of going right to Sinding you might still be stuck if the werewolf version is still in the cell (but it might be worth a try). If your on a PC and can start the quest with Mathis but it still gets stuck you could try console commands not sure how well it would work though.
i just entered the jail after the quest and sinding is making weird noises like white noise
Well i got a different issue and cannot find anywhere else where this has happened to anyone else it seems...he is not in the jail at all, i haven't spoken to him, i havent Seen him, i simply talked to the guy for the quest, walked into the jail, and he is not there, the quest marker points past the barracks when inside the cell room but trying to TCL over there results in me poping right back into the room on it's god damn own, so i cannot do the quest for the ring and might have to end up simply using a fkn console command to spawn in the ring and/or the hide.
Tried the commands that teleports me to him or him to me, and neither of the 6 IDs i've dug up, is recognised, altho making a clone of him, that sure works...unfortunatly, the clone does not count to talk to for the quest.
And no, i have no mods that would alter him or Falkreath as a whole.