You should still be able to use the old 3.6 console to run your reports. ePO 4.0 I am pretty sure uses a different DB schema and when you upgrade it starts a new db called ePO4_ServerNameHere.
You can just download the 3.6 console from mcafee download section and then add the database in the reporting section, then run your reports. You do not have to login to ePO in the console to run reports.
I doubt that you can logon to an ePO 4.0 server with an ePO 3.6.x console. You said you have upgraded the machine so there is no ePO 3.6x server service left.
ePO 4.0 has a new reporting section where you should also get your old report data (but not reports!).
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