@Fulton17: What version of Sabnzbd are you using now? Are you running it on Windows?
I just updated to 7.3 beta 1 last night and hit a problem with "repair failed, not enough repair blocks, (xyz short)"
Is this the error you get?
Sabnzbd is configured to automagically download par2 files to provide the repair blocks, and runs the repair automatically for you.
Sometimes, the repair fails, as in the above message, but you can manually run the repair, IF you actually have sufficient par2 recovery files. I managed to fix my repair error, manually, because there was one misnamed data file, which caused par2 not to scan the file, thus missing blocks of data. I forced par2 to scan all the files, and it worked fine.
As the OP suggests, if you are running windows, download the quickpar program, go to Sabnzbd's incomplete file folder, and run quickpar on all the par files, then if that is ok, run winrar to extract your data.
On linux my command is
par2 r somefile.vol*.par2 *