I finally had success!
I used the “HTTP Auth” task with “Method: Username and Password” prior to “HTTP Requests” task
| Field | Value |
|---|---|
| Method | GET |
| URL | https://myopenhab.org/rest/items/[item name]/state |
| Headers | %http_auth_headers |
| . | Content-Type: text/plain |
| Timeout | 5 seconds |