The browser you are using to connect to web client, does it recognizes the certificate as valid or invalid.?
Connecting to vCenter with webclient - valid
Connecting to ESXi with webclient host as the error message suggest - invalid
But after a break and cup of coffe I tried loged in to the suggested ESXi host
and installed the certificate, but not for computer, instead I installed
for user and finally works to upload the ISO-file.
Do you know if there is any way to "side step", as I think, not fully developed web client solution
for managing a VMware hypervisor.
if the certificate for vCenter is not located in the trusted root certificate authorities of the certificate store. this issue is reported.
If youn want to verify, check this from a new client and install the vCenter certificate in the truster root CA of the client.