It doesn't sound as if they would agree to mediation and you can't force it so I can't really understand the context in which the question is asked.
I agree with HildaW. Can you really not see anything that you might have said or done that might have upset them or been misinterpreted?
Fruit flies - help needed please.
Army horses loose on London streets
Have any of you got all electric cars? Pros and cons please.