Confused how to calculate e_t terms in ARMAX models

[jay katkani]

I have generated model.summary() from python, now i want to cross validate my model prediction using the equationin excel via that equation. So i am generating output in excel but i am not able to get the same results as model.predict() 

I am attaching the my excel sheet in my model 

i am using yt as meantemp and hummidity and windspeed as exogenous variable

I have developed SARIMAX(0,0,2) model

I think i am making some error in calculating e_t terms

In my excel sheet i have also attached model summary on left side 

Please help me in figuring out what i am doing wrong🙃

Excel link : https://docs.google.com/spreadsheets/d/1yRicuVWl9P0QQRG-PMKGthu0BowhFcsAAKSeAvs0cw0/edit?usp=sharing