Team, I did a fresh installation of Platform 8.3.1 and got into this issue.
1. the 831 platform admin password (upon 1st logon) change went thru.
2. Installed the Pega Foundation for Healthcare 83 - No Issues as far as installation /import screens concerned
3. Installed the v83 PegaHC.jar - No Issues as far as installation /import screens concerned
4. Four Sample jar of v83 Health Care - No Issues as far as installation / import screens concerned
5. On Pega Foundation for Healthcare 8.3 Installation Guide > " Optional: Configuring a ruleset for your custom code groups" > "1.Log in to the demo application using the administrator ID and password." As there was no admin ID of demo application mentioned (which operator name), the following steps were mistakenly done on platform admin's logon, leading to "In the Application rulesets section of the Edit Application window, click Add ruleset , and then type MyCustomRules in the field "
6. Went ahead with platform admin operator edit page Save, however the save did not succeed telling problems
7 Closed the platform admin edit page (Discard Changes)
8. That is it, now, upon logoff by Platform admin user itself I am getting led to this problem
9. Any new Sample Application Operator / User password change, though new password criteria accepted, upon submission, password never gets changed, the Pega branding navy blue page stays (Full screen navy blue of Pega branding), nothing else happens