The solution on this thread was...
If Back to Karkand is not working and have premium please reach out to EA Support they should be able to help you out with your issue.
How to contact EA support:
https://help.ea.com/en/contact-us/?product=battlefield-3-premium
Closing the topic.
And as i told to you and you can read in my post with red color, this is the reply that i got from EA support today...
the only solution was to delete my soldier and account and create a new again with bf3 premium
This solution is not good for anyone... repeat, i dont want to see that EAsupport transfer my games into a new account for fixing this error meanwhile there are persons that i contacted that joker solved their problems without transfering and loosing their accounts.
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After spending a lot of time testing, i got a workaround uninstalling firefox 72 and reinstalled firefox 52 that allow running battlelog plugin but lot of people told me that they are using firefox 72 without any problems...
At this time, im very lost about how to fix so perphaps the problem is about my pc...
Windows 10 PRO 1909
Corei7 sandy bridge 2600k
24gb ram
gtx1070
1hdd 500gb and 2ssd 500gb
Anyway, the solution told me after calling EA support was not good and im happy for not choosing because, deleting my account, soldier and progress, it wouldnt solved anything..
Please, how do you fix the problem for the other people?
EDIT: solved by an advisor