Hai,
I have RB751U-2HnD, just purchase few week, when I switch off the router than on back, the router cannot use. The LED only ethernet port 1 only light up (wifi and ethe 2(I connect to my desktop) not lightup) and I cannot connect to winbox.
I need to press reset button on router than the router can boot. Setting all reset, I need to restore setting back from backup.
I no idea why this problem happen cause before this I can off on without problem.
So any idea?
Newest Version of ROS on The Unit?
Did you Update Routerboot?
Mistry7
I’ve got about the same problem, 751U-2HnD, routeros 5.14, firmware 2.38. The board was working fine, I had to entirely change the configuration, finishing and backing up config, reboot, nothing worked but only eth1 led blinking. After a few attempts (reset, load backup, reboot) , it’s started working.
Try to downgrade to 5.12 version.
My router started to show the same simptoms after upgrading it to the 5.14 version.
See my comments on http://forum.mikrotik.com/t/v5-14-released/54472/67
Thank andrewwork, problem solve after downgrade to 5.12.
Just relize problem happen after upgrade to 5.14, already try many thing reinstall firmware, downgrade firmware to 5.13 but still problem.
If somebody face this problem but unable to downgrade becouse cannot login to winbox, you can use NetInstall.
So I think confirm new firmware 5.14 & 5.13 got bug with RB751U-2HnD. Just my 2cent 
nazree, auras, andrewwork
Please inform us about packages, that are installed on your routers.
Post here the output from /system package print.
751U with 5.13 packages. I have not succeeded getting the board working with 5.14 .
auras
Thank you very much for the information.
Do you use ipv6 and mpls packages? Is it possible to disable these packages for a test?
Update, everyone who had the particular problem. Please contact support with attached support output file.
The problem is fixed at 5.15 version, that will be released very soon.
We can provide you with pre-release 5.15 version.