Webform element can no longer be added - 8.x-1.0-beta4

I am using Webform (8.x-5.4) with Captcha and ReCaptcha (8.x-2.4) on Drupal 8.7.8. When upgrading Captcha from 8.x-1.0-beta3 to beta4 it is no longer possible to add a Captcha element to a webform.

Note at the time of creating this issue beta4 was not available in the drop down for the version number field on the new issue form - hence it is misallocated to beta3.

The scenario is:
Open a webform with no Captcha elements
Click on Add Element button at the top
Scroll down to Captcha in Advanced Elements and click the Add Element button next to it

The result is nothing is that the side bar of Webform to key details of the element added does not appear and the pop up form closes.

Let me know if any more information is needed.
Thanks