What infusion set are you using? If you're using a quickset, PLEASE look at the plastic cannula part that goes into your body. If you have them bent (they should come out perfectly straight no curve or bend) then that's why. If you get a no delivery, make sure you change EVERYTHING out (reservoir, insulin, and infusion set) because any of it can be the problem if it's not a bent cannula. The quickset and Mio infusion sets are VERY prone to this and if you have problems consider the Sure T (steel needle infusion set) and Silhouette infusion set (angled plastic, less likely to bend or kink on insertion). Call Medtronic's support line, they'll overnight you samples and ask for those. Also, if you do notice the bent cannula, ask for a canister and do NOT throw away any infusion sets with bent cannulas, save them, and send them off to medtronic. Always do this, do not let it slide. If it's not the cannula being bent, still get a canister and save ALL parts the reservoirs, infusion sets with tubing , EVERY SINGLE PART into the canister. The one I got was huge so I think you could fit a few full infusion sets in there I'm just saying.
I constantly had these problems on the short time I used the pump and I hated it because of this issue. I've sent them a complaint letter with the ones I sent back in a canister.