few thngs to try??
1 = Try your URL in a different Browser CHROME, EDGE, FIREFOX, BRAVE see if they all produce same message
2 = Scan any files you have on your computer associated with the site for virus/malware/trojan
3 = Remove the whole site and just add in INDEX.html page see what happens (create a new folder put your old site into that for safe keeping)
4 = If nothing happens with the index.html then try run the new folder see what happens if the warning appears again youve narrowed it down.