Conlog must be loaded after the SYS: volume has mounted. This is completed at the end of LOADSTAGE 1, so LOADSTAGE 2 is the earliest that CONLOG can be loaded.
To load CONLOG at the end of LOADSTAGE 2, create a file called INSTAUTO.NCF in SYS:SYSTEM. Put the desired CONLOG command (i.e. LOAD CONLOG MAXIMUM=1024 ARCHIVE=YES) in this file and save it. To load CONLOG at the end of LOADSTAGE 3 place the command in NASAUTO.NCF. Start the server normally and Conlog will load at the end of the appropriate LOADSTAGE and before running AUTOEXEC.NCF