I had the same issue.  First QuickBooks was insanely slow, then Lacerte wouldn't even open, for all programs.  For QB, it turns out the WebConnect file was corrupted, so i had to uninstall/reinstall just one prgram, and that cleared up that problem.  

With Lacerte 2018, I uninstalled it and reinstalled it, and that seemed to work.  With 2019, it just kept showing up in the taskbar but it wouldn't show on my screen.  I tried everything I could think of, then I right clicked on the 2019 icon, clicked on Properties, Shortcuts, and changed Run to Maximized.  

Voila!  That did it for me.  Hope this helps anyone out there, because staying on hold for an hour to get NO solution is something I don't wish on even bad clients I used to have.