Importing a private key

Hello. Help out, friends. On the JAXX wallet, any action writes the error TX-018. The funds are frozen and I can not do anything. Support has been silent for over a month. Downloaded and installed Litecoin core. I’m thinking of trying to import private keys from JAXX. You need to import private keys. I can’t figure it out. Help.When writing in the console, the importprivat key comes out “method not found - code 32601”.

Dude same thing for the last month