Go to file\administrator\components\com_virtuemart\plugins\currency_converter\convertECB.php
Find $document_address = 'http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';
Change it to https,$document_address = 'https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';
If problem remains the add, find$xmlDoc = new DomDocument();
add BEFORElibxml_use_internal_errors(true);