need help

• (pkttyagent:26630): WARNING *: 20:18:13.788: Unable to register authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of caller
  Error registering authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of caller (polkit-error-quark, 0)

what can i do now????