The specified file exists but is not a reduction-structure file as defined by ECHOMOP tasks. The most probable cause is that a data frame file name has been provided by mistake.
The reduction-structure file must be created before the reduction can proceed. The option/task ECH_CHECK_FRAME/ECH_LOCATE is currently the only one authorised to invoke reduction file creation so you should use this if you need a new reduction structure file.
Martin Clayton