Sorry, I misunderstood. Did you try re-entering the SN you got in your original 2017 email? I filled out the 2017 request form 3 times, each I received an email with the same SN I received with I first applied for SW2017. So I'm guessing that even if you did get an email, it would have the same SN as before.

For me, just using the modify option in add/remove programs didn't re-authorize. I had to go find the swactwiz_s.exe program and run that manually, only then did my installation get authorized. Its almost like the add/remove program thing only updates the SW serial number, but doesn't connect to the Solidworks mothership to re-up the license.

Anyway, sorry to hear you're having so many problems. Hope you get it working.