Hi and welcome to Justanswer.
Initially, did you try to replace your battery? If not yet can you please try to replace it now and see what happen. Slightly weak battery can not able to fully energized the solenoid inside to unlock the notch even you enter the correct code. Do not use rechargeable and used battery. Always use fresh lithium or alkaline battery only.
Let me know what happen.
Hope it helps.
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I'm just following up with you to see how everything is going. Did my answer help?
Let me know,Chester