Modernise All Button Not Working

At present, it would appear that the Modernise all button in the Modern section of the Audit tab isn't working.

Steps to reproduce:

1. Select Design Health and click the Scan Website button
2. Click the Modernise tab or click
3. Click the Upgrades Available panel
4. Click the 'Modernise all' button.

Actual Results

Clicking the Modernise all button doesn't appear to trigger any functionality that would fix all the safe fixes.

Expected Results
I would anticipate that clicking this button would fix all the safe fixes and list any remaining issues that require review.