Had an issue with Fidelity Advanced Trader (connection was blocked) and was also fixed by:
this solution from @Igor Kurzin
Make sure Windows Hidden files, is checked/ticked, refer: View hidden files and folders in Windows?
Open Kaspersky app, select Settings⚙, select General, uncheck Enable Self-Defense, select Save, select Yes - to confirm the action.
Exit Kaspersky app - on the Windows taskbar or hidden icons, rightclick the Kaspersky icon, select Exit.
Go to folder C:\ProgramData\Kaspersky Lab\AVP21.3\Report\ and delete the contents = all files and folders.
Start Kaspersky app.
Enable Self-Defense.
Shutdown the computer, using Shutdown, not Restart, power on, login.
Re-check the issue?
Just posting details regarding Fidelity to bump this up and hopefully help someone else if it happens to them.