Page PDF export does not work through the 'custom export'

Issue Summary

Page PDF export does not work through the 'custom export'. The site needs to be on the export version 2

Steps to Reproduce

1. Add a single dot in the section “Space Settings -> Look and Feel -> Title”
2. Export a single page from “Space Settings -> Space Export -> PDF -> Custom Export”, and select a single page.
3. Click “Export”.
4. The old PDF export version will be triggered. (the UI is of the previous export version)
5. 
   The export will be enqueued and one status shows up “Begin calculating the pages to be exported”.

Expected Results

The page should be exported

Actual Results

The export gets enqueued and one status shows up “Begin calculating the pages to be exported”.

Workaround

Export the page with the page export option available on top right corner page