@woolfg
That line appears to be in MB import format but without the " and last two compass points missing.
Is that your source file or the converter o/p ?
The converter would NOT recognise that as Cumulus data.
My test data was the few lines you posted earlier in the thread, and that works OK ....
01/09/18,09:00,16.7,90,15.1,0.2,2.6,99,0.0,0.0,1025.18,122.4,20.7,67,0.0,16.7,16.7,11.0,218,2.03,544.86,18.3,317,0.4,0,0.0,0.0
01/09/18,09:05,16.8,90,15.1,0.5,3.5,68,0.0,0.0,1025.25,122.4,20.7,68,3.5,16.8,16.8,11.0,217,0.10,544.96,18.2,331,0.4,67,0.0,0.0
01/09/18,09:10,16.9,89,15.1,0.9,3.5,68,0.0,0.0,1025.28,122.4,20.8,69,2.6,16.9,16.9,10.9,206,0.10,544.96,18.3,345,0.4,67,0.0,0.0
01/09/18,09:15,17.1,89,15.2,0.9,5.2,68,0.0,0.0,1025.35,122.4,20.8,69,5.2,17.1,17.1,10.9,152,0.10,544.96,18.4,359,0.4,67,0.0,0.0
01/09/18,09:30,17.7,88,15.7,0.9,3.5,73,0.0,0.0,1025.52,122.4,20.9,70,0.9,17.7,17.7,10.8,167,0.10,544.96,19.2,401,0.4,48,0.0,0.0
01/09/18,09:45,18.4,87,16.2,1.3,5.2,97,0.0,0.0,1025.58,122.4,21.2,70,0.9,18.4,18.4,10.7,250,0.10,544.96,20.0,441,0.4,92,0.0,0.0
01/09/18,10:00,19.3,85,16.7,1.3,3.5,178,0.0,0.0,1025.58,122.4,21.8,69,1.7,19.3,19.3,10.6,283,0.10,544.96,21.1,479,0.4,184,0.0,0.0
01/09/18,10:15,19.6,83,16.6,1.4,3.5,158,0.0,0.0,1025.62,122.4,22.3,68,0.9,19.6,19.6,10.7,309,0.23,545.08,21.3,516,0.4,240,0.0,0.0
01/09/18,10:30,19.9,80,16.3,1.0,4.3,167,0.0,0.0,1025.62,122.4,22.6,66,0.9,19.9,19.9,10.7,327,0.23,545.08,21.7,549,0.4,108,0.0,0.0
01/09/18,10:45,20.1,79,16.3,1.2,6.1,163,0.0,0.0,1025.72,122.4,22.9,65,0.9,20.1,20.1,10.9,341,0.23,545.08,21.8,581,0.4,117,0.0,0.0
Which converts to ..
"2018-09-01 09:00:00","16.7","90","15.1","0.3","3.8","99","0.0","0.0","1025.18","122.4","20.7","67","0.0","16.7","16.7","11.0","218","2.03","544.86","18.3","317","0.4","0","0.0","0.0","N","N"
"2018-09-01 09:05:00","16.8","90","15.1","0.7","5.1","68","0.0","0.0","1025.25","122.4","20.7","68","5.1","16.8","16.8","11.0","217","0.10","544.96","18.2","331","0.4","67","0.0","0.0","N","NE"