To get new permissions from a user, you need the target user to manually reauthenticate from the beginning.
You cannot refresh a token to get more permissions than that token originally had.
Additionally the validate endpoint is used to validate/give information about the current token. It is a read only endpoint and cannot be used to modify a token
Validate docs - get info on a token: Authentication | Twitch Developers
Refresh docs - reduce scope or maintain scope - Authentication | Twitch Developers
oAuth docs - get a new token with needed scopes - Getting Tokens: OAuth | Twitch Developers