If Rhino is frozen and you haven’t saved your file recently, DON’T FORCE QUIT RHINO.
Instead, use the next step to look for the autosave file. Copy this file to someplace safe, then go back to Rhino and force quit it using the Task Manager.
Rhino usually periodically autosaves a temporary backup called RhinoAutosave.3dm.
Location in Windows: C:\Users\[username]\AppData\Local\McNeel\Rhinoceros\X.0\AutoSave\
Folder is hidden by default. You can unhide files & folders in File Explorer by clicking View > Show More > Show hidden items. When done, don’t forget to re-hide them.
Don't open the file directly. Copy it to somewhere else like the Documents folder before opening.
Was the file opened directly from an email attachment (without downloading it first)?
If so, open Rhino and click File to see the list of recently opened files, along with their folder locations.
It may refer to a location such as C:\Users\[username]\AppData\Local\Microsoft\Windows\INetCache\Content.Outlook\E3XTHQXQ\.
Go to this folder using Windows File Explorer and you should see the missing files. Copy them to a different location such as the Desktop and then open in Rhino to check.
In the future, always save an attachment from Outlook first, and then open the saved file in Rhino.
Rhino saves a hidden backup file in the same location as the original.
Show hidden files to see. In Windows File Explorer, click the View tab > Show More, and enable ‘Hidden items’.
Filename is the same as the original but ends in .3dmbak. Remove the bak to use (also change the filename slightly so as not to overwrite the original).
If the file was saved in OneDrive, right click the file and choose 'Version history'. Use OneDrive in the browser (https://onedrive.live.com) to do this if local doesn't work.
If the file was in OneDrive but was deleted, use OneDrive in the browser to look in the online OneDrive Recycle Bin.
Update GPU driver and try again.
If still a problem, start Rhino in Safe Mode (see icon under start menu) and say no to loading plugins during startup.
It may complain about how it had to substitute a font. Resave file and see if that works.
Used to recover from the Datasmith Twinmotion plugin, which can cause Rhino to crash on start.
First try the plugin method above if a plugin is suspected.
Close Rhino.
Open the user account's Library folder (Option + Go + Library).
Under Application Support, delete anything starting with McNeel.
Under Preferences, delete any com.mcneel files.
Start Rhino and see if it works. It will require inputting the license info again.
Quit Rhino.
Open the hidden user Library folder (not the system Library folder).
Delete the following:
\Application Support\McNeel (delete folder)
\Preferences (delete two com.McNeel files)
Restart Rhino.