CWP User Panel php Version not changing

in CWP User Panel, I choose CWP Settings>Php Selector>Domain then change available php version to php 5.6.
I then click "Update version"

If i then refresh CWP User panel or choose a different menu option, in lower left hand menu i notice that the Application Version is still php 7.3.3

The php selector window is also blank again (ie no php version is displayed).

if i
1. Go to root user CWP Dashboard>User Accounts>List Accounts> select a user account>click on Edit and enable "Shell access" ,
2. Open a putty session and log in as one of the CWP clients User accounts
3. type php -v

It shows that this user (that i have changed phpversions for in CWP User panel) is unchanged

PHP 7.3.3 (cli) (built: Apr  2 2019 12:56:03) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.3, Copyright (c) 1998-2018 Zend Technologies

Something is wrong? How to fix?