Did you validated relay sha1 folder & if that file is available on your client’s immediate parent relay.
"BigFix Enterprise\BES Relay\wwwrootbes\bfmirror\downloads\sha1"
If its there validate the BESClient logs against your action ID, are you able to see
Download Available - "True" if so what further activities are happening there.
based on that you should be able to understand the problem !
Sometime it happen download is available or cached on your master server but till the target machines there could be multiple relays which also need to download that file if your connection between root to child relays & relay to client somewhere is slow or your package is too big it will take sometime.
funny thing, which we faced most of the time in such cases our relay started reporting to itself in such case download will never going to reach to the client until you not correct that problem.