I have same problems today!!
But we have different situation~
my situation is my customer ready to reinstall EMM 9.55,
they have dual emm server, so when i install external and internal
EMM, after I uninstall and reinstall EMM, the internal emm have same issue just like you!!
My solution is uninstall EMM again, but after uninstall you have to
delete the EMM and SQL file manually (C:\program files\mcafee and C:\program files\mssql).
After that, you have delete registry about "Mcafee EMM" manually too,
then you can reboot and reinstall EMM again!!