On page 74 of the DMG (Step 5: Consequences), it says that if you fail a skill challenge, it can become more difficult, such as detouring you in a different direction. Could you attempt the same challenge again at a higher difficulty? So, could you try 'talking to the ogre again,' but since it already knows what you want, it makes it more complex and you need to work harder for the answer?
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
As a GM, I would personally avoid allowing your party to rehash a skills challenge at a greater DC for both narrative and creative reasons. To elaborate your ogre example a bit, let's say the PCs quest is to rescue a group of villagers which have been captured by an ogre. The captain of the guard wants you to kill the monster, while the local druid sympathizes with the creature since his territory has been encroached upon by the growth of the village. In this case, the goal of your challenge would be to convince the ogre to release his captives through some non-violent means.
If your party fails to broker a peace, allowing a "redo" detracts from the dramatic weight of the skills challenge - where is the tension if the players can simply attempt a second round of negotiations? Failure needs to hold certain consequences in order to be meaningful, and win or loose, a skills challenge should always advance the narrative in some direction, not leave the party back at square one. Similarly, skills challenges are an awesome opportunity at collaborative story-telling between the players and the GM - you want to reward new and innovative thinking on the part of your PCs. Allowing your paladin to attempt yet another a diplomacy check isn't an especially creative approach to the problem presented.
Failing a Skill Challenge Should Be Interesting
DMG 76 says,
This means a DM should never introduce a skill challenge whose failure will stop the story (which is really what it means if they have to try it again and again until they win). Always have an interesting consequence that presents that party with an answer to "what do we do next?" It might be another skill challenge, or a combat encounter, or an intense RP session, but it shouldn't be "try it again, and do better this time." That's boring and frustrating for the players and the DM.
Despite the story-stopper, already pointed out, sometimes a retry could be allowed
Like a dead end cave, where a landslip had blocked the return path, and now the players must swim the way off. It's nice to see some char struggling to swim and hold the breath, and the multiple skills checks should be increasingly difficult every time they fails. In the end, the character dying or making it through the deep waters would have added a lot of tension.