It say:
~$ mactelnet d4:ca:6d:4:26:3e
Login: admin
Password:
Connecting to d4:ca:6d:4:26:3e…Connection failed.
~$
yesterday it work. but since one moment in time it have not worked.
reset configuration do not help 
the router is RB2011UiAS-IN
the RouterOS version is v6.38.5 (stable)
but today I have tried bugfix release without any success.
what happens and how it can be fixed?