Error When Pushing block ======> This Error Sucks!!

Recently I have been trying to run a steem node. waiting for it to sync for about a month
failed twice. and now getting this error. someone in my friends who is a witness knows how to solve this
please help me.

930866ms th_a       fork_database.cpp:44          push_block           ] Head: 13330826, 00cb698af39a4832539d01cde9f4ce1eb5d24bde
930868ms th_a       application.cpp:524           handle_block         ] Error when pushing block:
4080000 unlinkable_block_exception: unlinkable block
block does not link to known chain
    {}
    th_a  fork_database.cpp:64 _push_block

    {}
    th_a  database.cpp:625 _push_block