Gaining

It may be a level of impatience. Just pumping a lot of food in doesn't mean you're able to actually fully digest and process all of it.

Could have to do with gut health, muscle and bone mass, and what specifically you are eating. If its all empty macronutrient and very little micronutrient, then you're getting materials but not enough of the other things that facilitate the internal chemistries. Not that one needs to eat enough brussel sprouts to OD on vitamin A, but more... there is more that goes into this than increasing calories.

Hope that helps?

Your body may have to acclimate to the extra calories. Bodies seek equilibrium, and when gaining you're intentionally messing with that equilibrium, so there is always gonna be an initial inertial resistance.

Just a little bit of impatience it’s been 5 days keep up the consistency and you’ll see results.