I am using Android SDK Manager revision 23.0.5. I tried to update some SDK, but got this errors. I tried a lot of times. And I try to use \"https://\" in the option but failed.
To facilitate finding the clear cache on SDK Manager:
For SDK Manager 25.2.5 on Mac, select SDK Manager -> Preferences or press Command + ,
And there is the button to Clear Cache
However, I still cannot resolve my checksum error.
UPDATE:
The comment by @ded to this answer posts the link to the solution which worked for me.