Keypad is showing the following message:

 

INSTALLER EXIT FLTS

Z01 T Front door

 

Any idea how I reset alarm?

Looks like you have a tamper on that circuit. What has happened? 

I put the keypad into engineer mode and changed the battery in the front door sensor. I now cannot reset system. The main button on the panel is glowing red, not green.

I'd take the front door contact apart remove battery, make sure you have seated the battery correctly then try to reset again.

If the system still thinks the contact is in fault you can't clear down.

2 hours ago, Gary M said:

I put the keypad into engineer mode and changed the battery in the front door sensor. I now cannot reset system. The main button on the panel is glowing red, not green.

Front door sensor will have a small switch spring to show the contact has closed , probably you didn't close it properly or perhaps broke or dropped the spring or something along those lines