Vlookup doesn't work suddenly

Hi,

I need your help urgently. I have problem with this data validation on my spreadsheet.

There is a data validation in cell B2 (a dropdown list of items). Then, in cell C3, there is a formula "=VLOOKUP(B2,Student!A2:B10,2,FALSE).

It workes before. But something must've happened that causes it not to work now.

When i change the value of B2 from the dropdown list, the vlookup doesn't work anymore. I mean the value of C3 doesn't change.

Any ideas of what might happen. This is excel 03.

Thank you in advance

Thank you, Dave and JTP for your replies.

Yes, it works now. It's the calculation problem. For some reason, it's been changed to "manual" setting. As soon as changed it back to automatic, it works like a charm.

Well done.

Thank you guys for your quick replies