Pro Crash when opening new or existing file

I’ve been using a licenced version of Omnigraffle 5 (5.4.4 v139.18 t187838) for a few years without issue.
It suddenly stopped working a few weeks ago with the following crash report:

OmniGraffle Professional: objc[1512]: Class FileReference is implemented in both /System/Library/Frameworks/IOBluetooth.framework/Versions/A/IOBluetooth and /Applications/OmniGraffle Professional 5.app/Contents/Frameworks/GraffleShapes.framework/Versions/A/GraffleShapes. One of the two will be used. Which one is undefined.

OmniGraffle Professional: -[NSScriptSuiteRegistry aeteResource:] - the only supported language name is English.

OmniGraffle Professional: OSULastRunStartInterval default is non-nil; unless you forcibly killed the app and restarted it it should be nil at launch time.

I tried version 6 demo and it works fine, but I don’t want to pay again for this new version.
I tried to re-install 5, after removing all existing versions without success.
Any known solution to this issue?
Thanks.

I get this error to not matter what I do I can not resolve it.

Sorry to hear about the trouble. If this happened recently after upgrading to High Sierra, it may be a known issue. Apple has made changes that are not compatible with OmniGraffle 5. See https://support.omnigroup.com/high-sierra/ for details and options.

If you are using an operating system that should be compatible with OmniGraffle 5, try https://support.omnigroup.com/troubleshooting-crashes/ and feel free to contact us if we can help further.