I have a Named Box called CRNo which refers to cell Sheet1!$AU$2.

I then use this name to populate cells on other sheets, so I may have
cell B4 on Sheet2 set to =CRNo so that it fills with the same value as
Sheet1!$AU$2.

All straightforward so far.

Now, I have one sheet which flatly refuses to play ball. All I ever get
on screen is exactly what I type in the cell, e.g. =CRNo. It's almost
as if some recalculating is not taking place, but I don't know what is
so special about that particular sheet.
The text I have typed is identical to that on other sheets (I've even
tried a copy and paste). It just doesn't want to use the referenced
name.

Any suggestions much appreciated.