MikroTik

I have an old mikrotik router RB750. There was an old routeros version (3.30 or 3.something )
I want to make upgrade to last routeros version. I planned to go step by step, by main versions.
The 1st step was "system routerboard upgrade". It was done ok.
2nd step: upload routeros 4.17 and reboot.
After reboot it displayed info "You must upgrade licence". I click OK, it wrote something like "Upgrade licence was unsuccessfull." I rebooted RB and try it again. Everything it writes this message. (ping to internet is OK, it has internet connection)
I tried upload routeros 5.26 - upgrade was succesfull but there was still "wrong licence".
I tried upload routeros 6.34.1 - upgrade was succesfull but there was still "wrong licence".

Problem is, there is some time limit 70hours to upgrade, after that the licence will expire. But the licence upgrade is not working!

I think the recommended way was to upgrade to 3.30 first, from there upgrade the licence to support new longer software id, and once you have it, you can go directly to latest available version. I did that several times. I'd think the upgrade might also work in never versions, but I never actually tried that.

Yes, usually upgrade works normally. I did upgrade already on a lot of Routeros. But this is the 1st time, when I have trouble with the upgrade.
Can helps me please anybody from Mirkotik? I want not throw away hardware, which is normally working, just because some licence was not succesfully updated.

Thank you.

Yes, usually upgrade works normally. I did upgrade already on a lot of Routeros. But this is the 1st time, when I have trouble with the upgrade.
Can helps me please anybody from Mirkotik? I want not throw away hardware, which is normally working, just because some licence was not succesfully updated.

Thank you.

Hello Edoras,
Write an email to support@mikrotik.com, make supout file from this router and attach it to email.
Mikrotik Support should send you new license in a few hours.

Regards,
M.