Library Manager can't update index

Hi there,
Recent error message. IDE 1.8.5. (same issue in 1.8.0.). Can not update, remove, install and manage libraries (neither by the Manager, nor by hand).

An error occurred while updating libraries index!
java.lang.RuntimeException: java.lang.Exception: An error occurred while updating libraries index!
	at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onUpdatePressed$0(LibraryManagerUI.java:212)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Exception: An error occurred while updating libraries index!
	at cc.arduino.contributions.libraries.LibraryInstaller.updateIndex(LibraryInstaller.java:79)
	at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onUpdatePressed$0(LibraryManagerUI.java:209)
	... 1 more

I am at the middle of a development process and can not go further until a solution.
Please, let me know where is the problem and how to fix it.
Yours sincerely,
Tom

Timtomm: Can not update, remove, install and manage libraries (neither by the Manager, nor by hand).

Please describe what happens when you try to do it "by hand".