this will not fix nothing but you can see if Steam will start this way
Try Launching Steam using TCP
https://support.steampowered.com/kb...1b2e3f859d37772d13ed342b76&ref=1456-EUDN-2493
Start Steam with the "-tcp" launch option.
Please see the Setting Steam Launch Options topic for instructions.
Setting Steam Launch Options
How do I set Steam launch options?
https://support.steampowered.com/kb_article.php?ref=5623-QOSV-5250
Set Steam Launch Options
1.Navigate to your Steam installation (by default this is located at C:\Program Files\Steam)
2.Right-click on Steam.exe (this file is listed as an application and features the black and white Steam logo)
and select Create Shortcut
3.Right-click on the new shortcut and go to Properties
4.Select the Shortcut tab
5.In the Target: field add the launch options which you would like to use after the Steam.exe location (make sure to
separate all launch options with a space - For example, " -launchoption1 -launchoption2")
6.Click Apply and then OK to close the Properties window
-tcp - Launches Steam with the TCP protocol rather than the UDP protocol
also are you sure you set Windows Firewall to defalt settings?
do's F-secure use Windows Firewall i do not remember since the last time i used it you might want to remove/disable all
security software to be sure of nothing interfearing while you try to fix this
mabe Bitdefender changed something in the registry to block things and left it behind after uninstalling it
i'm sure running out of idea's
wish you luck
James