delete the computers adb key: rm /data/misc/adb/adb_key on device
(I have no idea if in case of multiple authorized computers the additional keys are in a new line of the file or if they are in new files. I have only 1 computer.)
stop all adb processes "killall adb" in linuxoids and "taskkill /IM adb.exe" in windows or simply the taskmanager in both.
restart the phone
toggle usb debugging off and on
connect
use adb
click authorize