Ember not being recognised in Website folder

I am working in a windows environment and have just installed ember-cli@1.13.1 as I am working on an existing project where we cannot upgrade to a newer version. everyone elses environment works fine but on my own workstation the following happens:

If I type C:> ember I get exactly what I expect, the standard listing of ember help topics. If I then navigate to my Website folder (D:>development\Jupiter.Europa\Website) and type the same thing (D:>development\Jupiter.Europa\Website\ember) I get the following:

D:\Development\Jupiter.Europa\Website>ember Path must be a string. Received null TypeError: Path must be a string. Received null at assertPath (path.js:7:11) at Object.join (path.js:466:7) at AddonDiscovery. (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\addon-discovery.js:107:24) at Array.map (native) at AddonDiscovery.discoverFromDependencies (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\addon-discovery.js:97:68) at AddonDiscovery.discoverProjectAddons (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\addon-discovery.js:45:31) at Project.discoverAddons (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\project.js:317:40) at Project.initializeAddons (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\project.js:336:8) at Project.eachAddonCommand (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\models\project.js:389:10) at module.exports (C:\Users\tpayne\AppData\Roaming\npm\node_modules\ember-cli\lib\cli\lookup-command.js:34:13)

Can anybody help?

Did you run npm install in your website folder? If so, also try deleting node_modules and running it again, in case of NPM unreliability.

Thanks, this seemed to work!