Where are you trying to login ? VC or ESXi host ?
Which credentials are used for accessing the machine ? local / domain credentials / SSO account
What is the version of VC ? Windows or appliance ?
Is it working when you launch webclient and issue is only with vsphere client ?
Tried with any alternate credentials ?
I am assuming you are connecting using your AD credentials? If so, how have you configured the identity source? Has the vCenter been added to the domain? Can you try to login using the UPN format for username (email@example.com)? Have seen this issue sometimes when "Active Directory (Integrated Windows Authentication)" is used in identity source configuration and using VCSA. And using UPN format works 100% of the time.
Are you using the firstname.lastname@example.org account? If so, the password for that account is set to expire after 90 days, by default.
If that's the case, perhaps this article can help you reset the SSO password for that account: https://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.security.doc%2FGUID-06FF691C-16EC-4AEF-BCE8-2438B51DE693.html