i use ESX 6 in my server And backup until last week had no problem But recently I get the following error :
Job Log: BEX_BEXEC_05225.xml
Final error: 0xe0009b61 - Backup Exec could not log on to the server with the logon account specified for it. The logon account does not have valid credentials. Ensure that the user name and password are correct in the logon account. Final error category: Security Errors
Try logging into the vCenter web client from the Backup Exec media server. If you're successfull, then in Backup Exec, go to Configuration and Setting -> Logon Accounts. Find the vCenter logon account (assuming you're using vCenter) and update the username/password to the one you just used.
Make sure that Backup Exec is using that account for the vCenter resource. Do this by double clicking the vCenter resource in Backup Exec then select credentials. You can use the drop down to select the proper credentials.
My suggestions should still work for ESXi as well. Just remember that ESXi is going to be case sensitive for the user as well. On the credentials page for your ESXI server, create a new Backup Exec logon account and use the ESXi user and password. If possible, copy and paste the username and password from the vSphere client.