Android 8.0 adb device keeps unauthorized after authorisation

Edit: I did some deeper investigation, but still no clue what causes the problem.

When I plugin my usb cable the phone asks: "Allow access to phone data"
I'm sure I have allowed the access but keep getting unauthorized

adb usb
error: device unauthorized. Please check the confirmation dialog...

adb devices
ce051605a5378d1b03      unauthorized

adb connect 192.168.1.6
unable to connect to 192.168.1.6:5555

Connecting over wifi also doesn't work, that is the correct ip as I setted it fixed.

What can be the cause and how can I fix it? Running on Samsung Android 8.0 and connected to PC Win7 x64.

Solution

If you're using Windows follow these steps, after i tried every solution and almost gave up i found the following and it worked.

First things first:
Phone: Check if you have a file called adb_keys located at: /data/misc/adb/adb_keys. If you have it, i would recommend you to backup the file. (I didn't have it.)
Windows: You'll need to have a file called adbkey.pub located at C:/users/UserAccount/.android/
Boot into recovery mode.
Plug your phone into PC.
Open cmd and run adb devices. It would show "recovery" instead "unauthorized".
Create a new file called adb_keys file on your PC:
```
type NUL > adb_keys
```
Now you need to copy the contents from the adbkey.pub to adb_keys, the new file you just created: adbkey.pub is located at C:/users/UserAccount/.android/ (Needless to say you need to replace "UserAccount" when running the command)
```
type c:\users\UserAccount\.android\adbkey.pub > adb_keys
```

Upload the adb_keys file to your phone:

adb push adb_keys /data/misc/adb/adb_keys

Reboot and run adb devices. It should be working now.

Thank mnoguti from this post on XDA-Developers for this answer.

If you have Linux that's the same solution with Unix commands.