Some more information would help.
What HANA revision are you on?
Sounds like you deleted the table directly within the catalog view? Tables created from a .hdbdd should only be deleted by removing the definition from the .hdbdd and the act of activating the edited .hdbdd will drop the table cleanly.
Also, "Table import target table cannot be found. Table import target table cannot be found." sounds like you didn't activate the .hdbti, as the repository version is still referencing your deleted catalog table. Is this the error preventing you from changing the model?
In the Repository view of the SAP HANA Development perspective is it still showing any artifacts like your CSV as deleted, with a red cross icon? If so, activate the deletion.