Hello everyone,
My colleague just experienced this issue and I'm wondering if there has been any revelations as to the cause or a recovery solution? He stated that he clicked 'Save' and then tried to X-out of Pro very shortly thereafter, which caused Pro and his computer to seize up, forcing a hard restart.
While the project is showing a file size, I am also unable to open it (receiving the same error as OP) via methods described above (copying to default Pro project location in Documents, opening from File Explorer, etc). We are both running 2.5.1, which is without question a newer version than that with which the project was created.
Thank you,
Derek