It looks like we lost the OpenDAP support for Windows users since version 2.7-1!
Are you sure that you update Windows binary packages to the latest netcdf with OpenDAP?

The following code snippet works perfectly fine on RNetCDF version 2.6-2 but not version 2.7-1 onward :-(

nc_url <- 'http://thredds.northwestknowledge.net:8080/thredds/dodsC/agg_terraclimate_tmax_1958_CurrentYear_GLOBE.nc'
nc_metadata <- RNetCDF::open.nc(nc_url)