I have to complete an assigment where I have to assign a dummy variable to 7 different classes. Those classes are divided on the frequency of social media usage and rated 1-7.

I created dummy variables with tabulate, generate.

However, when I run my regression I get an omitted variable. I ran my regression with 6 instead of 7 dummy variables and this still resulted in one dummy variable. Running the regression with 5 variables does not lead to a dummy variable, however I wonder if this is the correct way to do it.