Hello.
If you are on version 5.5 you have two clients on VMware vSphere.
The traditional VMware vSphere client (Windows App)
and the Web client
Download the vSphere Client
https://docs.vmware.com/en/VMware-vSphere/5.5/com.vmware.vsphere.hostclient.doc/GUID-B15F4221-ABDB-4...
Installing the vSphere 5.5 Web Client on a Microsoft Windows platform (2058262)
https://kb.vmware.com/s/article/2058262
To login using the web client you must have an older 32Bits browser that supports and has the Adobe Flash plugin installed,
both software must be installed without internet connection (temporarily) and configured so that they cannot be updated.
Personally I use the following combination, but only to manage VMware vSphere, to surf in the internet i use a more current browser.
Firefox ESR 38.8 (32bits)
Adobe Flash player 29.0.0.113
If what you lost is the root password, that's another issue.
Enrique Espinel
Senior Technical Support on IBM, Lenovo, Veeam Backup and VMware vSphere.
VSP-SV, VTSP-SV, VTSP-HCI, VTSP
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