MasterCook has never been designed for a NAS system.
If you wish to use it outside of its scope and intent, you are on your own. We will not provide support for you. You can follow the instructions below if you wish to proceed and work around it. Below is an example of how to get it to work with MasterCook 2020.
If only the user files have been stored on NAS there are two registry entries that need to be adjusted accordingly.
Registry entry 1 : HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\MasterCook\MasterCook 20\DocPath
Registry entry 2: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\MasterCook\MasterCook 20\ToolsPath
Their values will have originally resolved to the actual NAS path, for example Y:\\TROUT-NAS\SERVER-NAME\MC2020\UserFiles\MasterCook 20 (It will be an unusual long drive name). You will need to simply edit it to say Y:\MC2020\UserFiles\MasterCook 20 (Simply the drive letter Y: followed by the folders you have it in)
Similarly, for the toolsPath registry key you will need to edit it to simply say Y:\MC2020\UserFiles\MasterCook 20\MC Tools (Simply the drive letter Y: followed by the folders you have it in)
If you have the program files also stored on a NAS then there is one more registry entry to tweak.
After these edits have been made, launch MasterCook.