How to give reply to memo issued on me

Hi everyone I am a government employee working in a Municipal department Telangana state. Recently I got a memo from my Commissioner stating that negligence of performing duties. In memo it is written that out of five biometric devices, only one biometric device is working, instead of five biometric devices. So why don't we take action on you has per CCA rules. Now my explanation for the memo it is fact that out of five biometric devices only one is working The Other four was not working because the other for biometric devices are not working because it is a technical issue,which can be solved by biometric supplier. Even though I called the supplier to rectify the technical issue by that other four biometric devices will work. But the technical guys said it is Saturday we are out of office we can't help you now. Sunday is holiday. Monday I was not attended to the office because of my health issue on the same day you issued memo on me. Later I came on Tuesday and fixed all the technical problems of balance four biometric devices now all the five devices are working file. Please help me to write Above explanation in a neat and clean manner I mean office language. Thanks in advance