I am now obtaining the temperature and pressure with:

double Temp = C_T(cell,thread);
double Pabs  = C_P(cell,thread);

However, for some reason at the inlet the static temperature drops near to absolute 0 Kelvin in spite of the fact That I have set the total temperature as constant and the scenario is a 2D simple channel. I believe that the issue now is with the relationship between static temperature and total temperature. I use the isentropic relations for calculating one as a function of the other but in Fluent when I plot the total temperature, it loops over my enthalpy function. I couldn´t find any enthalpy-total temperature-static temperature in the Fluent guides (2019).

Regarding the UDRGM examples I used the one available at

where if I introduce the aforementioned functions for pressure and temperature lead me to the same issue that I am having. Therefore there isn't any fully functional UDRGM available in the theory guide that works with the newest versions.