Linking with equals sign doesn't always work

Trying to link a cell in one worksheet to a cell in another worksheet using
the equals sign. Sometimes it works, other times I get a #VALUE! Sometimes
it woks in one colum of a worksheet and not another. When it doesn't work, I
will sometimes get a 0 value instead of the #VALUE result.
The cell I'm linking to is a group of merged cells.
Any help