Need help with my Sound DD40.

It is missing the left side cab door and Bachmann will not sent me a spear door but say i must buy a complete shell.

Hoe can I fix this problem?

I live near Oxford UK.

I Got a very nice Bachmann 4-4-0 Richmond with factory fitted sound.

I got the loco very cheap $50 plus shipping to UK because it is/was a non runner.
When the loco is put on the track I get the stem hiss/pumping sound of  the air pump. I do not know the loco address.

The fault is the decoder.

I put in a blanking plug and the loco run very nicely on DC. I then put in a standard Bachmann decoder and again the loco ran very nicely.

My Digitrax Zephyr can not detect/read the decoder.