New CRS317 - bricked after Router OSv7 download?

RouterOS Beginner Basics
1

I got a new CRS317 today, part of my project to move my office to 10G. I am not a very experienced mikrotik switch user, I have some knowledge on RB4011 and CapsMan.
The Router comes with Router OS6, but I wanted to use the L3 hardware support. So, I started winbox, went to packages, choosed the 7.1.2 (testing) Firmware. Clicked on download (not on download + install).
The system answered that a reboot is needed. ok.
Waited 3min+ but could not connect to the switch again. Power-cycled the switch. No.
Tried reset to factory with the reset button. No.
Tried to run the netinst bootp loader by holding the reset switch a longer time. No.
Used a serial cable to connect to the console. That worked, I got a prompt.
I set to boot to Ethernet. Now the switch MAC address showed up in the netinstall program. I choosed the firmware I previously downloaded from mikrotik. But after sending the command no sucess prompt.

Back to the serial console after a power-cycle I tried what happens if I boot from the NAND (this is the default I guess?)

RouterBOOT-6.47.10
What do you want to configure?
   d - boot delay
   k - boot key
   s - serial console
   n - silent boot
   o - boot device
   r - reset booter configuration
   e - format storage
   w - repartition nand
   g - upgrade firmware
   i - board info
   p - boot protocol
   b - booter options
   j - boot os
   t - test ram memory
   x - exit setup
your choice: x - exit setup


writing settings to flash... OK


RouterBOOT booter 6.47.10

CRS317-1G-16S+

CPU frequency: 800 MHz
  Memory size: 1024 MiB
 Storage size:  16 MiB

Press any key within 5 seconds to enter setup.....

loading kernel... bad section header
 kernel not found
trying bootp protocol........................................................

I am not sure about if I myself or the device is responsible for the bricking, but If If could get it back to a usable configuration, that would be good. Can I flash the kernel without losing licensing information?

Anyone with an idea what to do next?
TIA

2

Try installing ROS 6.49.3 via netinstall. After it successfully reboots, perform routerboot upgrade (under system → routerboot). Routerboot is similar to BIOS and older routerboots can’t always boot new kernel that comes with ROSv7. And routerboot 6.47 is a couple of years old.

After you upgrade routerboot, try to upgrade ROS to v7 … and if it boots fine, don’t forget to upgrade routerboot again.

3

Thank you mkx,
I tried 6.49.3 already, but this did not make it better. I also tried an older version of netinstall, but this did not even connect to the switch/the switch did not got an IP from the bootp server.
Then I used a different pc with the newest netinstall etc. etc.
Everything went through without a hitch.
The PC which worked uses windows 2004
The PC which did not work also, but is a notebook (Dell 7280).
Both have a real ethernet card, both have firewall disabled.

Go figure what the real problem has been.
Good to have a serial console, but bad that you ever need it. I am looking forward which obstacles occur next.