If you forgot the sapadm password on the server where your SAP Host Agent password is running and are no longer able to validate the landscape configuration for this node, you can reset the password for this account on the server.
(note: the 5 first steps are copied from the section "Windows server" of the SAP KBA 2512232 - How to reset sapadm (SAP Host Agent) password, version 1)
- On the server where the SAP Host Agent is running, click on START, Run, and enter lusrmgr.msc into the Run dialog box then click OK.
- Next locate the sapadm user account, right click on this account and choose set password
- Enter the new desired password
- Go to Administrative Tools, Services, then open the properties of the service SAPHostControl
- Click on the logon tab and update the password as set in step 3 for the account sapadm
- Restart the SAPHostControl service
Thank you Toby