The document “*.graffle” could not be opened. If this document was created by a newer version of OmniGraffle, it may use a format that this version of OmniGraffle does not understand

I cannot open older documents Graffle talk ist is for e newer Version.

I have MacOS11.3 and Graffle 7.18.5. I think the Document is createt on version 6.x

Pls help it is a very big document and it is it is many work to rebuild it.