How do I fix my Optima mx6 alarm?

I have recently moved into my house, I was given the code to my optima mx6 alarm by the previous owners but no manual. since then the mains have tripped and when I switched the mains back on the alarm sounded both from the control panel & outside. I tried putting in the code but this has no effect, the only way I could turn it off was by removing the fuse. It may be the code I was given was incorrect, the previous owners confirmed this code but said they did not use the alarm very often. Either way could someone advise me how to fix this