Control Panel > General > Post Likes Settings

does your forum have a limit on likes per 24 hours?
maybe the user used up all of those likes in that period.

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NOTE: "Allow Members to Like Posts in Locked Threads" is available as of UBB.threads 7.7.5

Current developer of UBB.threads PHP Forum Software
Current Release: UBBT 7.7.5 // Work In Progress: soon
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