If you're on a Mac running a newer OS (Catalina or Big Sur) and are unable to download Serum presets via the Splice desktop app, this error is likely the result of a permissions issue with the destination folder that Serum presets download to.
To resolve this, check the folder permissions for the Splice folder in your Serum presets folder. Open Finder and go to:
Macintosh HD > Library > Audio > Presets > Xfer Records > Serum Presets > Presets.
Once you're in the "Presets" folder, right-click/CTRL-click on the "Splice" folder, and then go to "get info." At the bottom of that menu, under "Sharing & Permissions", make sure the "privilege" next to your Mac account name is set to "read & write." If it's not, please change it to "read & write," and then try downloading a Serum preset again via the Splice app.
If the issue persists, please go backwards in that above filepath, and make sure every enclosing folder in the path is also set to "read & write," using the same method as above to adjust permissions if necessary.
If you're still experiencing issues, please contact us as firstname.lastname@example.org. Please be sure to include your Splice username/email address and computer/OS details when writing in!