adb sideload does not transfer data
adb sideload does not transfer the file to the sdcard permanently. To sideload correctly, you need to pick that option from the recovery first and then when the phone is waiting for the sideload type,

adb sideload &lt;PACKAGE&gt;


If you want to push the file to the phone's sdcard, you could try,

adb push &lt;PACKAGE&gt; /sdcard/


That should copy the file over to the sdcard. Keep in mind that there is no progress bar.

EDIT: Try the following to restart the adb server,

adb kill-server


then,

adb start-server


Then check if the instructions work again.