Honda CBF 125 seat lock not opening

[JONH00]

I'm having an issue with my CBF 125 rear seat lock. I purchased the bike two months ago from a private seller and I've never had the rear seat opened up. I've tried to do this today to fit a top box but the key isn't turning in the barrel and unlocking the seat. I have the spare key for the bike, neither work in the lock, but both work in the ignition. The key turns about 3mm before it stops and won't turn any further.

Does any one have any clue how to get this lock open, either by conventional methods or not? I can't see what's causing it to catch or why it wouldn't open. Any help would be much appreciated!
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JON H

[ForestRunner]

If there is stuff stored under there, tools etc, they may be fouling on the release catches.
Try jiggling the seat pad while the key is turned to see if you can dislodge whatever is there. Once it's off, repack carefully

I had similar issues when a spare bag and some zip ties vibrated into the wrong place...
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Slowly learning...
CBF125 Red (Stolen) -> CBF125 White -> 1999 Hornet