Do you have an active PS plus membership? Also check out this [url=https://www.bungie.net/en/Help/Article/11931]link[/url] on help with getting your NAT configured.
https://www.bungie.net/en/Help/Article/12280
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Cam5465 is most likely correct. usually when you cannot get in to a crucible match and there is no one in the tower it is because your NAT type is too strict. Follow the link cam provided for more information.