Alarm after battery change

Hi lads.
Due to unforseen issues, my accord has been sat since November and the cold weather killed the battery. I replaced it today but the alarm is constantly going off and the glow plug light is flashing when the engine is running. Ive tried unlocking and locking the car over and over but it hasn't worked. Could someone shed some light please. Thanks
Accord 2004 ictdi executive

Your alarm control needs to re-sync with the MICU. With new battery and car unlocked, lock with the key fob. Wait around 15 secs, indicators will flash rapidly to indicate successful re-sync. then unlock again.

The alarm battery could also be dead, in that case you will need to go into the drivers side rear wing remove the alarm and fit one of these replacement batteries,
https://cellpacksolutions.co.uk/products/batteries/gp-batteries-gp320bvh6a6-siren-alarm-box-sab-battery/

Thanks lads. I tried a few things before your suggestions. I fired it up, cleared the flashing glow plug light and left it running for about 20 mins and had a drive around the block. It soon went off and has stayed off

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