There are a few possibilities when you experience no connection or no download.

The station is a serial data logger so it need to connect to correct serial port. On conventional PCs this is the 9 pin D connector. Serial is always the preferable connection as it is hardware controlled and not a software device such as USB. However today most consumer PCs and all lap tops come without a serial connection.

If they are using a USB to serial adapter then they need to have installed the drivers that came with the adapter. This will create a VCP (virtual com port) and again they need to know the port number it creates. The driver software will usually tell them this otherwise they can find it from their Windows Device Manager > Ports.

Once they do this communication should be OK.

Very occasionally we hear reports that the station stops receiving data. This is usually because something has affected the data logger, possibly an electrical spike. If t logger interval is rest (using the HeavyWeather software) this seems to solve the problem. If it does consider fitting a ferrite to the cables to absorb future spikes.