The URL must be missing some values, or they have been wrongly defined.

Make sure you use the following syntax when adding the variables
Eg.*Layers&Area Data&Area Style&*Bounding Box&Map Size

Area Data (ad=) has not been defined
This is to determin which areas will be symbolized specifically on the map in the format ad=layer name:a:area code1|b:area code2 etc
You can have information form more then one layer defined by using || as a seperator
Eg ad=layer1 name:a:area code1|b:area code2||layer2 name:c:area code1|d:area code2
The layers can only be earth, tdwg1, tdwg2, tdwg3 or tdwg4. Click on the name to see a list of the area codes.

*Bounding Box (bbox=) has not been defined
Bounding box defines the viewing area within the map.
The numbers are based on Long/Lat coordinates
bbox=minX(minimum point Longtitude),minY(minimum point Latitude),maxX,maxY
Eg. bbox=13,-13,31,5 will give you a map showing the Democratic Republic of Congo.
bbox=-180,-90,180,90 is the full world view
If Bounding box is not defined the map will default to the extent of the area data being requested (ad=)

Map Size (ms=) has not been defined
This defines the size of the map that will be displayed.
It can be only a single number representing the width of the image. The height is that number divided by 2.
eg. ms=1000 will give you a width of 1000 and a height of 500.
Or it can be ms=width,height where you assign both values.

Area Style (as=) has not been defined
This defines the Area Data called earlier and fills in the color and optionally the border size and color
Eg as=a:00ff00 will make the ad (area data) defined by a: the color green
If you wish to do more then just color:
Eg as=b:ff0000,0000ff,2 will make the ad (area data) defined by b: the color red (ff0000) and draw am outline with the width of 2 around its borders in the color blue (0000ff).
If you want to assign only a value (without changing the color) for border you must still format it like this
as=c:ffffff,0,4 This will make the ad (area data) defined by c: the white (ffffff) and draw am outline with the width of 4 around it.

* Items are optional
Please refer to the wiki for how to setup the service: