I removed all the impex files from my server in an effort to uninstall it.
Later, I upload all the files again to reinstall it.

now I get this error message:
Unable to add cookies, header already sent.
File: /home/freerxin/public_html/impex/ImpExFunction.php
Line: 522

Is there a way to fix this?

Nevermind seems to have worked itself out.