Is it just a problem with a variable name or could be more than that. for example data issues!!! Everything is ok with the SPSS results. Need help. Thanks.
That error message likely indicates that "X" doesn't appear in the data set that you have loaded/linked to AMOS. Any "rectangle" variable is presumed to be a manifest/observed variable, and therefore appear in the data set.
If the variable "X" is latent, measured by several items, you can convert it into an observed variable by collecting the items through the "compute" window in SPSS.
In Amos, The unobserved (latent) variables should be represented by a circle, while the observed variables should be represented by a rectangle.