We have multiple accounts. When making a query using the JSON API, devices for only one account are returned. I tried to specify the &metasearch=custid:<custid>& parameter like the user interface use...
It sounds like you're experiencing an issue with the JSON API not returning devices for multiple accounts when using the &metasearch=custid:<custid>& parameter. This could be a limitation of the API or a configuration issue. I recommend reaching out to the support team again to investigate further and escalate the issue if necessary.