I think we have found the origin of your issue. Your 808 project name includes a slash (/):
808 Claps FX/HD. Spark does not handle it correctly, instead it interprets it as a folder separator (as used in paths). For this reason, the project folders hierarchy is corrupted and instrument can't be imported from it.
We will fix this issue in the next upcoming update, but in the meantime you can re-save your project using the "save as" command in the Spark toolbar, renaming it without any slash character. Then you'll be able to import instruments from it.
Hope this help, let us know