If you try to open a Central File in REVIT and you are NOT using the same version (and Build number) of REVIT that was used to create the Central file, the 'Create New Local' option is not available, greyed out or disabled.
a) If you are using an older version of REVIT then you are hooped and cannot open the file, period. Go away.
b) If you are using a newer version of REVIT then just open the file, upgrade it to your version of REVIT (done automatic) then 'save as' the file and click the 'Option' button in the Save dialog box and check off the option for 'Make this a central file after save'.
Then you need to close this new central file and relinquish everything.
Lastly you can now open the same file and the 'Create New Local' option is BACK !
I have seen this problem where the REVIT version is the same but the culprit is the 'Build Number'.
Also if this is / was a central file that has been relocated to a new folder the 'create new local' will be grey out or disabled. You need to make it into a central file again. Just open it anyway, then do a saveas click the 'Option' button in the Save dialog box and check off the option for 'Make this a central file after save'. Then you need to close this new central file and relinquish everything. Then try to open it again and notice the 'Create New Local' should be available.