Hi Tejas,
Most common reason to that error is when you don't have SSL certificate for your vcenter, your certificate is invalid or it's generated for different hostname that the one actually used when configuring VIO. If that's the case, and if you are using VCSA, you might want to regenerate the certificate using the admin panel of VCSA.
The other reason might be that time is out of sync between management server and VCSA. Please check what's the time in VC and management server, if they are out of sync, enable NTP or adjust time manually.
Hope that helps.
Best Regards,
Karol