Hi,
i have bought some software from Ebay with all the codes etc, and bought the carsoft 7.4 interface, when i connect a window comes up "communication error". I have checked the leads and not all the wires are connected to the 32 pin lead and also the obd connector. Can anyone help with this.

It clearly states on the Carsoft site that:

"Carsoft does not allow its products to be sold on eBayŠ or any other online auction or bulletin board site."

How much did you pay? I assume legit versions are thousands of dollars.

You bought the cheaper, basic, non-"multiplexed" interface. It won't work with the OBD2 connector that came with the kit. For that you need the more expensive interface that I have seen on eBay for as little as $220 and as much as $360.

The interface you have is very useful for '96 and later cars with the 38-pin diagnostic connector, but you will need to improvise. The necessary information can be found on another forum. See here: http://www.benzworld.org/forums/r129-sl-class/1315950-diagnostis-later-cars.html?