The following article should help you debug problems where when you discover devices your lambda function is not called. It should also help you debug why your Alexa Smart Home Skill works in one region and not others, or why certification failed even though the skill seems to work for you.
In order for Alexa to successfully "discover" those devices though, the skill endpoint must be hosted in the AWS datacenter associated with that language. If they do not match, device discovery will fail and the certification team will reject the skill. Thus it's possible for device discovery to succeed in one language version of the skill, and not another. Here's an example:
- en_US: NA (US East N Virginia)
- en_GB: EU (EU West Ireland)
- de_DE: EU (EU West Ireland)
For instance, if you have a Smart Home Skill in both en_US and en_GB you will need to have both an NA and EU endpoint defined. The NA endpoint should be US East N Virginia. The EU endpoint should be in EU Ireland.