I had a similar case recently: Are you sure that the resource is linked? There are two ways:
- .res resource: In this case, your form unit must contain the line {R *.lfm} after the "implementation" keyword.
- .lrs resource: In this case, your form unit must "use" the unit "LResources" and have and "initialization" section with the line {$I <unit name>.lrs}
If you cannot find any of these lines, add the {$R *.lfm} after "implemenation".