CDO

I have pretty strange issue, I have this netdf file which is making me mad:

netcdf test {
dimensions:
        ncells = 196608 ;
variables:
        double lon(ncells) ;
                lon:_FillValue = NaN ;
                lon:standard_name = "longitude" ;
                lon:units = "degrees_east" ;
                lon:long_name = "longitude" ;
                lon:axis = "X" ;
        double lat(ncells) ;
                lat:_FillValue = NaN ;
                lat:standard_name = "latitude" ;
                lat:units = "degrees_north" ;
                lat:long_name = "latitude" ;
                lat:axis = "Y" ;
        int64 time ;
                time:standard_name = "time" ;
                time:long_name = "time" ;
                time:axis = "T" ;
                time:units = "days since 2017-01-01 00:00:00" ;
                time:calendar = "proleptic_gregorian" ;
        double tprate(ncells) ;
                tprate:_FillValue = NaN ;
                tprate:coordinates = "lat lon time" ;

which appears to be incompatible with CDO. I cannot understand which metadata is missing since I get

cdi  warning (set_coordinates_varids): Coordinates variable time can't be assigned!
cdi  warning (cdf_read_xcoord): Unsupported array structure, skipped variable tprate!
cdi  warning (cdfInqContents): No data arrays found!

Any hint on what is wrong? Is there any documentation for getting info on which CDI info are required by CDO?
Thanks for any help!