If you upgrade or recompile FreeBSD kernel and it won’t boot up properly, you need to boot with old kernel and do the recompiling again.
To boot with previous version of kernel, reboot the server, select option 6 “Boot Loader” from the menu. In the promot try
unload
boot kernel.prevor
boot kernel.GENERIC
boot kernel.old
To see list of available kernels, use “ls boot“.
