Problem publishing a tModel

Hello,

I am trying to publish a tModel through NWDS from a certain Web Service Definition but when I do that I receive this error:

An ERROR has occurred

Invalid key passed: Unknown TModel key in reference. TModel key :uuid:c1acf26d-9672-4404-9d70-39b756e62ab4

Why is that and do I have to publish the WebService inside a tModel in order to reference it from the Client Side? Also, a bit of explanation regarding the tModel and why do I need it will be very helpful... 😊