When using vlookup fuction - not looking up numeric only data

=IF(ISNA(VLOOKUP(A3,'Inventory Items'!$A$3:$D$888,'Inventory
Items'!$C$1,FALSE)),"",(VLOOKUP(A3,'Inventory Items'!$A$3:$D$888,'Inventory
Items'!$C$1,FALSE)))

it will lookup A3 if it is a alpha or mixed but will not if it is numeric
only. Do I have to change Cell A3?
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Thank you