The solution has been posted several times in this thread.
go here
https://github.com/rm-you/p99-login-middlemand/releases
click the p99-login-middlemand.zip file and download it and extract the .exe from within and put it somewhere
do the steps in the Instructions: section of that page to modify your eqhosts.txt file
run p99-login-middlemand.exe that you extracted, you'll see a black box, ignore and minimize that
launch p99 as usual