Based on our internal testing, this error will only be encountered when a Constituent record already has Constituent Appeals at the time of import. Constituents where the import does not error will have the Appeal and the Package imported properly.
If you encounter the above error and have recently changed your User Options, please restart RE7 and attempt your import again. If you continue to encounter errors after restarting RE7, please contact Support for assistance.
Screen shot of the User Options for Appeals: