I can’t seem to activate Rage in App or on Web

Just as the title says, I can’t seem to figure out why I don’t get the drop-down to activate Rage. I’m not even sure where the drop-down box is supposed to show up… attached character.

Neebash Barbar

I can tell you where it is supposed to be, but when I viewed your character sheet and tried it, it was missing.

Click on Features and Traits.

Find where it describes Rage, and click anywhere on it.

A sidebar opens. Scroll all the way to the bottom of the sidebar, that's where it is supposed to be, but is missing when I tried to do it on your character sheet. I checked one of my players' characters, and it works there, so they didn't remove the feature... but I will say that we have found it to be EXTREMELY buggy. Sometimes it's there, sometimes it's not.

I spent a bunch of time with the same issue.  I figured out that it doesn't seem to show up for Characters created before the feature was added.  If you create a new Barbarian character, the rage toggle option shows up.

Quote from Dachmingen >>

I spent a bunch of time with the same issue.  I figured out that it doesn't seem to show up for Characters created before the feature was added.  If you create a new Barbarian character, the rage toggle option shows up.

It is not about when the character was created. It's only available on the 5.5e Barbarian class, not on the 5e Barbarian class. These are implemented as separate classes on D&D Beyond.