Why do i got 401 error server response?

followed by instruction, I was created Self Client and generite token with ZohoCRM.settings.modules.READ scope. after php request i got this

array(4) {
  ["code"]=>
  string(13) "INVALID_TOKEN"
  ["details"]=>
  array(0) {
  }
  ["message"]=>
  string(19) "invalid oauth token"
  ["status"]=>
  string(5) "error"
}
int(401)

i do not understand WHY...