Open an articulate storyline 360 file which it says is corrupted

I have a storyline 360 file which after an update to storyline can not be opened. It says there is either a security issue or it has been corrupted. However, I can view all of the slides in storyline when I try to import but can not physically import them. Therefore I think it isn't corrupted but has messed up security.
I have already tried
1) searching for previous versions
2) Checking temp folders
3) renaming and importing
I am willing to pay 25 pound for investigating and a further 50 pound ONLY if the file is successfully opened for me in storyline. So you will receive 25 pound no matter what but only the whole 75 if I can open the file.