A lot of companies have poor setup in dealing with email enquiries. Often the emails just get lost or are not treated as serious. Perhaps the person dealing with email enquiries does not pass them on (?). One reason for this can be the volume of spam and emails. Spam is destroying email communication and even if a spam-filter is used it still is a nuisance.

Not defending a lack of response as detailed here, just possible explanations.

Sometimes the telephone or fax machine works entirely better. Walking in in person too if that is possible.