I'm running a freshly installed vCenter Server 6.5 embedded on a new ESXi host. There's no problem logging into vCenter SSO with the default administrator-user. However, I've tried adding a new user but I'm simply not allowed to login with it, I've added it to all the administrator-groups in vCenter too for the sake of testing. It's in the same local domain as the administrator "@vsphere.local" (which I'm using to login as well) and for simplicity I've even given them the same password. It's not joined to any AD or such, just local users. But all I get is "Invalid credentials" when I try to use it.
I've tried everything I can imagine, is there something else I might have missed? Are there logs anywhere I can check for what's actually wrong?
I could add images etc, but adding a user and logging in shouldn't be rocket science, setting up everything else has not been a problem.