Locate a good *.bin (usb, ftp, flash, nvram, etc)
=-=-=-=-=-=-=-=-=
switch: emergency-install <path:filename.bin>
<cr>
=-= or =-=-=-=-=-=-=
switch: dir flash:
switch: more flash:package.conf <== verify if good
switch: boot flash:package.conf <== boott once verified good
<cr>
=-= or =-=-=-=-=-=-=
switch: boot <path:filename.bin>
switch: boot
<cr>
note: once device is up, configure/convert to "INSTALL" mode (use install add file...)
References
Recover Catalyst 9000 Switches from Upgrade Failures – Cisco
Troubleshoot Rommon on Catalyst 9000 Series Switches – Cisco