RestClientException: Could not extract response. no suitable HttpMessageConverter found

The main problem here is content type [text/html;charset=iso-8859-1] received from the service, however the real content type should be application/json;charset=iso-8859-1

In order to overcome this you can introduce custom message converter. and register it for all kind of responses (i.e. ignore the response content type header). Just like this

List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();        
//Add the Jackson Message converter
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();

// Note: here we are making this converter to process any kind of response, 
// not only application/*json, which is the default behaviour
converter.setSupportedMediaTypes(Collections.singletonList(MediaType.ALL));        
messageConverters.add(converter);  
restTemplate.setMessageConverters(messageConverters);