The error indicates the required database driver (a .jar file) cannot be found.
What database are you trying to import from? The default embedded one (hsqldb) or another database (MySQL/Postgres)?
If it's the latter, did you place the driver in jre/lib/ext, and set up a Configuration.xml file for the project?
In reply, you're welcome to attach the project's Configuration.xml file, as well as the platform configuration (Help>About>Installation Details>Configuration>Copy to Clipboard) and log (View Error Log button in the same location).
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