Log Shipping: Unable to change from Standby mode to No Recovery mode I have tried to change the mode from standby to no recovery in log shipping environment. But the restore job fails automatically. And it did not change to restoring mode. Can anyone help me to resolve this?
If I understand correctly, that is not possible as you described it.

Kendra Little described the actions that are available to you.  Please read her article at:

https://www.brentozar.com/archive/2015/01/reporting-log-shipping-secondary-standby-mode/

A couple of important points:  


Logs Restore More Slowly if You Use STANDBY (Readable) Mode
Everyone’s Kicked Out When You Restore Transaction Log 


So, you get to choose between (1) slower restores for STANDBY MODE and (2) having faster restores, with the penalty of losing the connection.