The way you write, i'm not sure if i get it, but ...
If the Selection Info Palette is not inside the Palette area together with other's, then seelct that Palette on the top and drag it to about center of Palette area, then there should turn up a sort of cross, move the cursor over to center of this and leftclick, then it should jump in again.
There was also one version where we need to doubleclick on top of Palette to make it jump in, dont remember if that was in v 2017.
If non of this 2 options work, go to Tools/ Cusomize >> Palettes and turn of everyone of them, then turn them on again in the way you want them to be placed in TC like from left to rigth in default/ horizontal or from top and down in forced vertical, OK and out of menu.
If they now are like you want them, og back to Customize >> Options on left side and save the cfg (UI) ( in about middle of that menu) with a name of your choice that are NOT one of the standard names, if you not already have made a personal.
Click yes if TC ask if you want to change.
Now, next time if something happens with your cfg (UI) setup yo can go back to Customize >> Options and Reload your personal cfg (UI) very easy.
V20, V21, 2015/ 16/ 17/ 18/ 19 Pro. Platinum
Deluxe 2015/ 16/ 19
Windows 10 Home Premium 64 bit, 32 GB
NVIDIA Geforce GTX 780m, 1 GB