Response cache : Cache_miss error, caching not working

[saikrishnadandu]

I am using the below response cache policy in the proxy preflow  and the cache is not getting hit, please help what could I be missing here

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ResponseCache continueOnError="false" enabled="true" name="RC-Test -Caching">
<DisplayName>RC-Test -Caching</DisplayName>
<Properties/>
<CacheKey>
<Prefix/>
<KeyFragment ref="request.uri" type="string"/>
</CacheKey>
<Scope>Exclusive</Scope>
<ExpirySettings>
<ExpiryDate/>
<TimeOfDay/>
<TimeoutInSec ref="">3600</TimeoutInSec>
</ExpirySettings>
<SkipCacheLookup/>
<SkipCachePopulation/>
</ResponseCache>