Faulty ovulation test

My husband bought me a digital ovulation kit a few weeks ago. I just reached the 10th day of my cycle...so started testing yesterday. So far..I've used 4 strips over the last 2 days and all 4 have thrown error codes. I'm doing everything exactly according to the instructions. I clearly got a faulty test. I took it to the Safeway where he bought it, but without a receipt, they won't exchange it for a new one. So basically we just threw $30 away and didn't get any answers. And now he's gone to work for the next 48 hours...and we more than likely missed my window b/c the test is garbage. What a disappointment and waste of money.