Hi Michaela,
Please follow the following link that will help you to recover the corrupt file, and please let me know if you are able to open it or not.
https://ansyskm.ansys.com/forums/topic/how-to-restore-the-corrupted-project-in-ansys-workbench/
https://www.padtinc.com/2013/07/16/corrupt-ansys-mechanical-database-you-might-be-able-to-recover/
Regards,
Sampat