Does a transaction with a lock time need more time to be confirmed? I've made this transaction in the testnet:

https://testnet.blockexplorer.com/tx/2f18c646a2b2ee8ee1f295bb5a0f5cc51c5e820a123a14b0c0e170f9777518bb

It's a multisign tx with locktime. The locktime has expired and the tx is signed, but it isn't confirmed... Does somebody know why this tx isn't confirmed?

Thanks
Mempools are constantly changing. Each node has its own policy (how much of it to keep, when it gets cleared, which ones stay when a block is found, etc) so it's difficult to know if your transaction is on the network. Generally, you can be sure that a tx with a sufficiently high locktime won't be in the blocks before that locktime, but you are not guaranteed that it will be in the blocks after for a lot of other reasons (insufficient fee and mempool turnover being the two big ones). Generally with these types of transactions, it's recommended that you broadcast after the locktime has passed.