How to renew NPM12 maintenance with license key without Internet access?

You need license manager and following orientation in screen for to resolution .

Do you mean Web Based License Manager? Didn't seen offline option there ;/

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Activate licenses offline

1. On the Activate Product window, select This Server Does Not Have Internet Access, and click Next.
2. To finalize your registration, click Copy Unique Machine ID.
3. Paste the data into a new document in a text editor, and save the text document.
4. Transfer the document to a computer with Internet access. For example, transfer the document to a shared location.
5. Log in to the SolarWinds customer portal and find your activation key:
   1. Browse to https://customerportal.solarwinds.com from a computer with Internet access, and then log in using your Customer ID and password, or your individual user account information.
   2. Browse to the SolarWinds product, such as Network Performance Monitor, and click Manually Register License.
   3. Provide the Unique Machine ID you transferred earlier, and download your license key.
   4. Transfer the license key to a shared location.
6. Return to the offline computer where you have been running the activation wizard, and browse to the shared License Key File location from the Activate Product window.
7. Click Next to continue, and complete the Activation wizard.

"   see more here    Activate your SolarWinds license    @jaroslowLAdyga

Thanks, I cutted all links and switched OFF switches and when server was really off then I've got the option :-)