Veritas R8 Alarm won't reset but beeps when using the external doors, pleas?

Last week we had a series of power cuts, the Veritas R8 alarm hasn't been used for a long time. When the power went off it kept beeping for 20 minutes then went off. Now the power is back on but it won't reset (the keypad is less responsive and doesn't do much). When we use the front or back door the alarm beeps for about 30 seconds before stopping. Please can anyone help?

JJ
June 2017