Out-of-date Cambium metadata variable prevents downloads from working

[cpaulgilman]

When SAM downloads pricing data from the Cambium API it stores metadata from the API in a variable to populate the input options. As the Cambium API is updated over time the metadata changes. If you try to download Cambium data after the API changes, the downloads fail with an API error message.

See https://sam.nrel.gov/forum/forum-general/4649 for details and a workaround solution.

To fix the problem, SAM should display a message if the stored metadata is different from metadata from the API so that the user knows about the changes.