In a new project of mine I cannot see the Deployment Assembly link in the project properties. It is There in my other projects which are configured in the same way (as far a
Solved this with two simple steps
right click on the project > Build path > configure build path > Project facets then make sure you have the Dynamic Web Module checked
right click on the project > run as > run on server
then you could see the error is gone by going back to
Build path > configure build path > Deployment ssembly