Offsetting of AP amounts in Different Currencies on one account

Please can anyone help, I Cannot offset one vendo with 3 different transactions posted against it with 3 different currencies on it error" Currency code EUR with triangulation No after the has no exchange rate."

Silly question but does the EUR currency code have a valid exchange rate covering the transactions to allow the conversion of X to home and then home to EUR?

Yes we do but you cannot have more than one currency for triangualtion