So we onboarded a few new ESXi servers with Datto RMM network discovery. If the credentials are incorrect, you will actually face a lockout issue on the ESXi host where you will not have access to the user interface.
The first thought that went through my mind was that i needed to go and reboot the host, which wasn't even a viable option as this was a production server running many server VMs.
The first thing to determine is if you actually have the correct credentials, which will be the same as the host login. Since this ESXi host was an HP ML350, i was able to access it with iLO from the backend. Then i connected to the host via HTML and logged in.
This gave me hope as to this is just an issue with the UI, and i don't have the wrong creds.
From here what i did was enable the ESXi shell on the host, and toggled to the shell command line. From there i reset the management interface with the following commands.
After this was complete, i was able to successfully login to the web browser once again. This essentially achieves the same as restarting the server, but has no outages for the running server VMs.
Let me know if this helped anyone out!