If you post the transaction's ID here the community might be able to help.
Very old versions of multibit were capable of sending transactions that included something called high s values. Since then the Bitcoin network has been changed to only accept transactions with low s values. If your wallet sent a high s value transaction the network will reject it.
Upgrading to the latest multibit classic version will solve that problem
https://multibit.org/releases/multibit-classic/multibit-classic-0.5.19/There is a problem with Multibit Classic where the transactions with high "S" values are not accepted since the Bitcoin protocol is now enforcing low S values only. So my question is will the developers and maintainers of Multibit upgrade classic to use only low S values when sending Bitcoins?
I hope they will since I like the classic wallet better than HD. I would hate to run into problems where my transactions would not be accepted by the network.
Besides that problem the network has a high backlog of transactions. Any transaction without a very high fee per KB is likely to take longer than normal to confirm.