Nuke fails to launch and displays a message saying 'Cache disk size lock failed.'
Nuke is not able to launch if it cannot access or write to its disk cache location. This may happen if you set Nuke's cache location as a local drive on your machine which is then removed or if you accidentally set it to a location that doesn't exist.
The location for Nuke's disk cache is saved within Nuke's preferences. If you have set the disk cache to a custom location and Nuke no longer runs then you can fix the problem by manually editing the 'preferences10.0.nk' file in the '.nuke' directory within your home area and removing the diskCachePath line.
NOTE: If you're running into this problem with an older version of Nuke then you need to edit the preferences file for that version, e.g. preferences9.0.nk for Nuke 9.
If you haven't specified a location for Nuke's disk cache in the preferences then it will fall back to using the location set by the NUKE_TEMP_DIR directory. If you're still getting the error message then please try unsetting the NUKE_TEMP_DIR variable or setting it to a different location.