I am working with a panel data set in Stata 16.1 that has 14,690 observations and 19 variables. I am running regress on a dependent variable of policy stringency index, which varies by day during the 130 day study period, and a series of independent variables. My main independent variable of interest is World Bank income classification groups, which is a time invariant categorical variable. Several of my other independent variables - used as controls - are also time invariant. I want to know the coefficient for each of these time invariant independent variables as well as use a fixed effects model to capture the other time invariant effects. However, I am struggling to create a fixed effects model that does not omit my time invariant independent variables. My current code is:

Code:
xtreg strin_ind i.income_cat i.n_polity over65 covid_cases_prev_day ghsindex i.date, fe
Stata omits all of my independent variables except for covid_cases_prev_day. I have seen studies that treat the other time invariant independent variables as controls - how can I do this?

Thank you!