Use a Bitcoin block explorer to check if the closing_txid is visible. If it's not, the transaction might not have been broadcast properly or might have been dropped from the mempool. If the transaction isn't in the mempool, you can try rebroadcasting it. LND has a command called rebroadcastclosingtx that allows you to rebroadcast the closing transaction. This can be useful if the original broadcast didn't propagate through the network properly. If the transaction is stuck due to a low fee, you can use Child-Pays-For-Parent (CPFP) to bump the fee. This involves creating a new transaction that spends the unconfirmed outputs of the stuck transaction with a higher fee, incentivizing miners to include both transactions in a block. Sometimes, issues can be resolved by communicating with the owner of the remote node. They might be able to help by broadcasting the transaction from their end.