Problem with AP 2802 fail to join WLC

[cripy192]

hello I have a problem.
I try to join an ap 2802 to a wlc 5520 but I can't do it I get the following error in AP

IN AP 2802:

show capwap ip config
IP Address : 192.168.240.234
IP netmask : 255.255.255.0
Default Gateway : 192.168.240.3

Primary controller IP : 192.168.240.3

Primary Boot Image : 17.6.1.13
Backup Boot Image : 17.8.0.144

--------------------------------------------

in WLC:

Version: 8.2.170.0

IP: 192.168.240.3

[Leo Laohoo]

On the WLC, post the complete output to the following commands: 

1. sh sysinfo 
2. sh time

NOTE:  Do not post screenshots.

[cripy192]

Manufacturer's Name.............................. Cisco Systems Inc.
Product Name..................................... Cisco Controller
Product Version.................................. 8.2.170.0
Bootloader Version............................... 1.0.20
Field Recovery Image Version..................... 7.6.101.1
Firmware Version................................. FPGA 1.7, Env 1.8, USB console 1.27
Build Type....................................... DATA + WPS

System Name...................................... WLCNEW
System Location..................................
System Contact...................................
System ObjectID.................................. 1.3.6.1.4.1.9.1.1069
Redundancy Mode.................................. Disabled
IP Address....................................... 192.168.240.3
IPv6 Address..................................... ::
Last Reset....................................... Power on reset
System Up Time................................... 315 days 10 hrs 57 mins 31 sec s
System Timezone Location......................... (GMT -5:00) Eastern Time (US a nd Canada)
System Stats Realtime Interval................... 5
System Stats Normal Interval..................... 180

--------------------------------

show time

Time............................................. Thu Jan 7 18:11:39 2021

Timezone delta................................... 0:0
Timezone location................................ (GMT -5:00) Eastern Time (US and Canada)

NTP Servers
NTP Polling Interval......................... 600

Index NTP Key Index NTP Server Status NTP Msg Auth Status
------- ----------------------------------------------------------------------------------------------

[Leo Laohoo]

Look at the time and date of the logs from the AP.  They are wrong. 

The controller has no NTP settings and the time-and-date of the WLC is also wrong. 

Set up the correct time-and-date or enable NTP and the AP should start to join.

[Kasun Bandara]

Make sure time and date of WLC is correct

[Arshad Safrulla]

APs that are upgraded to Release 17.6.x cannot join controllers that are running AireOS versions earlier than 8.10.162.0, 8.5MR8, or 8.5.176.2(IRCM).

https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-6/release-notes/rn-17-6-9800.html#:~:text=Warning-,APs,-that%20are%20upgraded

You need to manually downgrade the AP via tftp by connecting a console if SSH access is not available. Check the compatibility matrix and download the correct code for your AP and then downgrade it manually. 

archive download-sw /reload tftp://<TFTP_IP_ADDRESS>/<FILENAME.TAR>"