Find the missing element in the series.
$$\text{TB, LA, ?, PY, RX}$$

Wait, let's look at the question text carefully: JB, LA, ?, PY, RX
Let's correct the question according to the prompt text:

$$\text{JB, LA, ?, PY, RX}$$

Let us look at the first and second letters of each cluster separately:
1. First letter sequence: $\text{J, L, ?, P, R}$
* $\text{J}=10$
* $\text{L}=12$ ($10+2$)
* $\text{?}=12+2=14\to \text{N}$
* $\text{P}=16$ ($14+2$)
* $\text{R}=18$ ($16+2$)
The first letter increases by $+2$. So, the missing first letter is $\text{N}$.

2. Second letter sequence: $\text{B, A, ?, Y, X}$
* $\text{B}=2$
* $\text{A}=1$ ($2-1$)
* $\text{?}=1-1=0\equiv 26\to \text{Z}$
* $\text{Y}=25$ ($26-1$)
* $\text{X}=24$ ($25-1$)
The second letter decreases by $-1$. So, the missing second letter is $\text{Z}$.

Thus, the missing element is $\text{NZ}$.