Thank you for your KB-post.
The procedure to change the password for the user prtgadmin is the same on a standalone Core Server, on a Master Node and on a Failover Node. However, this needs to be done on every node, where you want to change this password. Otherwise it will remain on the default password.
- Open the PRTG Administration Tool on the node where you want to change the password (in your case: on the Failover Node)
- Switch to the tab Administrator
- Reset your password for the user prtgadmin
- Save&Close the Tool
For Master nodes and Standalone Server only
- Login to PRTG Web GUI
- Head to Setup > Account Settings > My Account
- Set your individual password for the user
This can not be done on the Failover node as long as it is in read-only mode. So here, it's possible to reset the password from "prtgadmin" to a randomly generated password "only".