allmost all map works with mobile xt if you get gsp signal first
First picture tell me that you do not have correct ID
i make this file can you test it ?
you can try to put sd-card to nuvi and look sd-card cardID and use it in sw.unl
if you keep finger in nuvi battery icon about 10sec can you go secret menu, here is sdcardID if it open in that model "data card test page"
EhCCxZ2Ffe4]http://www.youtube.com/watch?v=EhCCxZ2Ffe4
I do not know if this works your nuvi 855
Or can you see in about screen both numbers
Device ID
&
Card ID
????