Rock shox pro delux rear shock

[Brendan goldie]

Good morning guys , I've just bought my self a giant dh team downhill bike to start . Received the bike on Wednesday and ran threw it last night checking everything out to find my rear shock was as if I had a pogo still on the rear of the bike . I have taken the rear Rock shox out to find when I compress the shock it does not return any reason for this ? Is it an expensive fix ? How does one fix this , please advise . Thanks a mill