With Mac OSX 10.13.6 It suddenly happened that a midi track in the score editor, in edit mode the writing appears, but in page mode it disappears, it can be printed but without pagination or editing control as it does not it looks, the screen appears black, the page and the staves do not appear, I am desperate, I have reinstalled in Cubase 10.5.12 and the problem has not been solved.
Help please.
Your data is probably safe, so you can take a breath. 
What I would do in this situation would be to create a new midi track, and copy the the midi part in question to the new track, so you can start from scratch in the Score Editor Page View.
If that doesn’t fix it, then start Cubase in Safe Start Mode and delete preferences.
The data is saved, thank you, I started Cubase in safe mode and it remains the same, I tried to reinstall Cubase and it remains the same. Total despair.
I’ve also cleared the preferences, and it’s still the same.
Did you
I have done what you tell me and even more. I have deleted all Steiberg files related to Cubase, following the Steinberg page recommendations for .plist and .bom files. I have gone back with Cubase installations, installing 9.5 again, updating to 9.5.50 and I still get the problem.
Really I’m desperate, I have consulted with My Steinberg Help and they do not give me a solution. They just tell me to update my operating system and Cubase 9.5.50 is compatible with my OSX. I am bitter and very angry, a lot of money I have spent with Steinberg since Cubase 5 so that for the moment they simply tell me that. 
Anger obviously does not go with you.
Very Thanks
Companions, mates, problem solved, I uninstalled the Acrobat Pro 9.0 which seems to be incompatible on Mac Osx Hig Sierra with the Cubase … Amazing.
Thanks for everything my friends.
And if someone says that Cubase 10.5.12 is not compatible with OSX Hig Sierra 10.13.6 does not tell the truth, I am using it without any problem.