You might be familiar with the term "gender dysphoria," which means
"psychological distress that results from an incongruence between one's sex assigned at birth and one's gender identity." Simplified down to a far less technical wording, it means "being unhappy with the gender you were born with," however it is often compartmentalized to specific things. Facial hair might cause unhappiness for trans women, an inability to grow it could cause unhappiness for trans men. This is how dysphoria manifests, and could be anywhere from minor sadness to even suicide. Yikes.
So if dysphoria is bad, and euphoria is the opposite, it seems fairly obvious what gender euphoria is. Simply put, gender euphoria is happiness with things that you like about yourself that match your gender identity. For example, wearing a dress for trans women, or wearing a suit and tie for trans men. As physical transitions progress, this may include growing breasts for trans women, or having them removed for trans men. This can be anything from small pleasure to a bit of a "high" that comes from being elated. Simple enough, right?
But what if you feel neither? What if you don't feel bad about what you have, but also don't feel happy about it either? Is a neutral feeling normal?
Yes, no matter what stage of transition you may find yourself in. Obviously if you are considering transitioning, and aren't sure if you are transgender or not, this is a fairly good indicator that you might be cisgendered (or "having a gender identity that matches what you were assigned at birth"). If you do not feel gender dysphoria prior to transition, and thoughts of being a different gender do not give you gender euphoria, it is HIGHLY advised to deeply consider if you are transgender at all, and if you decide to transition, proceeding with an abundance of caution.
But if you've already started transitioning, and find neither displeasure in what hasn't transitioned yet, nor pleasure in what has, don't fret, this is a VERY normal part of being transgender. Yes, you can still be transgender even if you don't feel dysphoria nor euphoria. You've already started transitioning, and unless you have plans to detransition because you weren't in fact trans after all, this more than counts. Early on in my transition, I often found the mental changes alone had me a bit complacent in where I was. This wasn't because I felt no need to continue transitioning, but rather that continuing to progress in and of itself is where I found the most comfort. Comfort doesn't need to make you happy or sad. Feeling normal in your own skin is its own reward.