LTC Status: Status 0/ unconfirmed, not in memory pool

Dear all,

Im not able to send LTC from my Litecoin Core Version v0.14.2 Wallet to a trade marketplace.
See below the data of my last attempt.
Transaction fee: -0.00226000 LTC
Net amount: -0.48837000 LTC
Size: 226 bytes

The blockchain is updated.
The status is still 0/offline. I tried this now 3 times and waited 3 days for the first try.

Any suggestions?
Thanks in advance.