Thanks, oddly enough, that worked! I uninstalled SSMS 18.4 and all SSDT components. Then, installed SSMS 17.9.1. Installed SQLPrompt SUCCESSFULLY! Then installed SSMS 18.4, uninstall/reinstall SQLPrompt SUCCESSFULLY! Now I am too scared to uninstall SSMS 17.9.1 because that being on my system is apparently the only reason I could install SQLPrompt 10.0 at 10:30 PM today, 13 hours after I started trying.
I'd be really insterested to see if anybody else had this issue. I contacted RedGate directly about it, but I don't think I got a response.
I would not uninstall 17 for now ... the issue is with a registry so I will keep as you said both for now... Many of my colleagues skip the update of SQLPrompt so they don't have to suffer like us...
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