You can simply hit the break key when it is starts booting up and go to rommon mode. If break key does not work by anychance try ctrl + c while its start booting up,
Once it is in rommon mode you can check for the file in flash and can manually boot the router and set the boot path and config register value to 2102. If the problem persit it is mostly a problem with the file which you can then format the flash and xmodem the file and boot it manually and set the boot path and config register value.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...