It is very odd that you were able to download from your Dropbox Jim, apparently there has been a protocol change with the Dropbox app and AcuDesign has not been updated to continue to be integrated. I am getting the “Dropbox.com error 400 as well. Janome it seems has REALLY dropped the ball on this one. I am irritated that my free app does not work as it should, but I am angry that my lettering module that I paid $49 for is now USELESS. Something that was so easy is now a headache ........READ THIS: On September 28, 2017, API v1 will be turned off, so it's time to move to API v2.
If you want your app's Dropbox integration to keep working, upgrade to API v2.
For details about the deprecation, check out the blog post.
Please acknowledge that API v1 is being deprecated by clicking the box below. If you do not acknowledge that you're aware of the deprecation, your app's users will be notified as part of the deprecation timeline.
I understand that API v1 is being deprecated
I'm aware of the API change, as I have removed Dropbox from our apps that use it. My iPad is using iOS 11, which supports app extensions. In that situation Dropbox is managed externally from the AcuDesign app. This is also available in iOS 10, but not iOS 9, which is where many of the free iPads given with 15000s are stuck. I can't speak for Janome, but it's possible that they did not want to spend the money to have the app revised to use the new API. They may deal with it in a future update, rather than doing it now.