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The Liquidity Setting setting tells the computer how generous or frugal with the stock the management wants it to be. The setting needs to be correct on the particular unit that the order is made up on.
Declining usage
The usage is decreasing, and the computer's calculations show that the SoH is sufficient. The user may remember the previous high usage and think that the item has been 'missed'. Look at the stock card, and consider the usage.
Database corrupted.
More rarely, a corrupted database can prevent items being ordered. This should not be considered until the above causes have been eliminated. Fix by doing a compact of the database, and if that fails an overnight rebuild (ask the help-desk about this, deails in the 'Agents help').