Can't switch to PC platform

Questions & Answers
1

98501-bluzijr2rp24ifinj3kleg.png"Switch Platform" button is disabled for PC standalone.
Reinstalling Unity from 5.6 to 2017 didn’t help.
And there was no option for PC standalone in Download Assistant.
98500-rfzkexb-tru9nc6dzbe9uw.png

2

Fixed with full uninstalling Unity and cleaning preferences, registry.