Python SDK not auto-refreshing token despite config

Trying to let the SDK handle the refresh automatically instead of writing my own loop. The docs say:

“The platform client will automatically refresh the access token when it expires.”

But my requests are still failing with 401 after an hour. Here is the init code:

client = PureCloudPlatformClientV2()
client.set_access_token(‘my_token’)

No refresh token is being passed, but I assumed the SDK fetches it? It doesn’t seem to be doing that.