Hi Chris,
You can download LW 4.18.8 basic from the link in my first post - if you had bought Pro & your Pro benefits have expired then you wouldn't be able to download from your Pro personal download page.
But the free basic 4.18.8 is available for download by anyone

Even if it's only the basic version, if you can get that to work then it'll be some indication of whether the problem's version related. And there's not much difference between Pro & basic anyway.
If you want to keep trying with LW then go for the basic. If you don't want to try any more then no worries
If your old LW was here one day & gone the next, maybe one of your security programs could be a problem. Some people have found that their antispyware program would (wrongly) pick LW as a threat & delete the .exe file. Which security apps do you use?