Hi Peters,
I also have Voxalot set up as gateway 1 and have the following in my dial plan:
|<#1:>xx.<:@gw1>|
I just dialed #1600 and it went to the Echo test as expected.
Try removing the comma from your plan. Also what happens if you dial 600 or *600 for echo test?
I also tried |<#1:>[*x][*x].<:@gw1>| which also worked
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