TL;DR: Twilio does not recognize your account SID / auth token pair. Re-copy both from the Twilio console (watch for test vs live credentials and stray whitespace) and retry.

```text
twilio.base.exceptions.TwilioRestException:
HTTP 401 error: Unable to create record: Authentication Error - invalid username
```

## Fix it

1. In the Twilio console, copy the live Account SID and Auth Token fresh. Expected: exact values.
2. Check you are not mixing test credentials with the live API base (or vice versa). Expected: consistent set.
3. Set them without extra quotes or spaces; in env vars, echo the values to check for strays. Expected: clean values.
4. Retry the call. Expected: 201 Created, not 401.

## When this applies
- TwilioRestException with HTTP 401.

## When it doesn't
- HTTP 404: the SID format is fine but the resource (number, message SID) does not exist.
- 400 with trial messaging errors: trial account limits, not credentials.

## Compatibility
- twilio 6.x/7.x/8.x.

## Why it happens
The auth token is a password; any mismatch 401s. The console shows the token once clearly, and copy-paste through docs and chat apps frequently corrupts it.

## Edge cases
- Rotated tokens invalidate old ones immediately; update every place the old token lived.
- Subaccount SIDs need the subaccount's own auth token, not the parent's.