Problem: We need a tool to generate the serial key used in issue #4715 (Activation dialog which also accepts a serial key).

Solution: Create a key generator which encodes the customer name, edition, company name, email address, account expiry date.

Web server now generates this serial.

Problem: Online activation (email/password) can fail for a number of reasons, but often the user is left wondering why.

Solution: When online activation fails, recommend the user tries offline activation (serial key).

The activation was successful for me in Windows 7 but the application still shows '(unregistered)'.

Appears to be fixed in 1.8.1-beta-f7377d6, both 32- and 64-bit windows versions tested.

Also note that the serial number is available for entry on the first screen.

Working for me

Version: synergy-v1.8.1-beta-f7377d6
OS: Windows 7 64 Bit

Still an error/issue on Windows 10 Enterprise 64 bit.

Worked as expected.
OS: Linux (Fedora 24)
Version: v1.8.1-beta-f7377d6-Linux-x86_64

A-OK. Win 7 x64

Working as expected.

OS: Windows 10 64bit
Version: v1.8.1-beta-f7377d6

OS: OS X El Capitan V10.11.5
Version: v1.8.1-beta-f7377d6

Working as expected.
OS: Debian Jessie (8.5)
Synergy v1.8.1-beta-f7377d6

I can verify the error posted by @SpaceRangerWes. But the serial suggestion does still work.

I can also verify the error posted by @SpaceRangerWes on Windows 10 Enterprise 64-bit, v1.8.1-beta-f7377d6. And that serial suggestion still works.

working as expected:
OS: windows 10 pro
Synergy v1.8.1-beta-f7377d6

Works for me:
OS: Windows 10 64bit (Client & Server) & 32bit Windows 10 Client)
Version: synergy-v1.8.1-beta-f7377d6

Valid timed Key: ns.dll is loaded

There are some cases when it works and when it does not.
SERVER system info:
Windows 10 Enterprise x64
CLIENT system info:
Windows 8.1 Pro x64

Version: synergy-v1.8.1-beta-f7377d6

For e.g.: If I use probably non existing user email as test@test.com and any random password - it notifies me that login failed and once I close that message it asks if I want to use key instead.
However, if I use existing user(I've used my own that is registered in Synergy, but it does not have any valid subscription) - then wizard will not prompt me to use key..

I'm not sure if it should ask every single time login fails, but currently it asks only once while you stay on the same ACTIVATE wizard step. I mean if you go back to WELCOME step and then go Next and try to fail login again, it will suggest you to enter key instead.

OS X 10.11.5

when I turn off internet connection:

Amac Keylogger Pro Serial Numbers. Convert Amac Keylogger Pro trail version to full software. Perfect keylogger.

after clicking on OK it just disappears. However after I restored internet connection clicking on OK resulted in prompt if I want to use serial key.

looks good OSX 10.10.5 after 3rd try

Windows 10 Pro
synergy-v1.8.1-beta-f7377d6
Works as expected. I do see the 'FATAL' errors as reported by @SpaceRangerWes, but they are not fatal in that the dialog window remains functional. On third attempt the messagebox offering the serial key appears.
As noted by @aj4mq, the serial key option is available from the first screen.

On Mac OS X 10.11.5.

I get the prompt as expected. I then tried using the serial key from the Issue #4715 test. After the plugins are installed, synergy closes. I know this was not part of this test but might this be a problem?