Error : "Couldn't connect to any seeds"

hi, i create tendermint cluster with 4 nodes that one node is validator and the others are non-validator. then non-validators seeds set to node_id and ip of validatos node in config.toml file of each non-validator nodes.
suppose node0 is validator and has node id “ID0” and ip address “IP0”. in config.toml of other three nodes i set : seeds=“ID0@IP0:26656”. cluster seems work correctly and transactions commit and query each of nodes is ok and “curl -s localhost:26657/status” has same results in each node. (same height)
but three non-validator nodes log error=“coudn’t connect to any seeds”. how i can fix this error? thanx