Authentication failed with status code 401

When trying to sign into on prem Bitbucket, it fails with status code 401

**To Reproduce**
Steps to reproduce the behavior:
1. Go to Atlassian Settings
2. Click to enable Bitbucket
3. Select Other Options
4. Add Bitbucket Site
5. Add credentials
6. Click on Save Site
7. See error**Expected behavior**The plugin logs in with the provided credentials

**Screenshots**

**Environment and Version (please complete the following information):**
- Atlassian Plugin Version 3.4.17
- Visual Studio Code Version 1.98.2
- Is this a local or cloud environment? Local
- If Local, OS Windows

**Additional context**
This has stopped working since version 3.2.0

Reproduce the failure through Atlassian Settings: enable Bitbucket, choose Other Options, add the on-premises site and credentials, then select Save Site. The issue names no source file or test, so first locate the Bitbucket sign-in flow and determine why the provided credentials receive status 401; done means local Bitbucket authentication succeeds on the stated environment.

Written by the indexing model from the issue text.