Hello Taha
Keep in mind that the AnyConnect client depending upon its version can support various different configurations. You may have configured the ASA exactly the same way as in the lesson, but the client may or may not support certain configurations.
You may also find that depending upon your operating system or connecting device (Windows 10, Windows 7/8, Android, iOS, Mac etc…) you will have different capabilities. The following Cisco community thread describes some of these issues that have resulted in the same error as you are getting here. Hopefully this will shed some light on the problems you are facing:
Let us know how your troubleshooting is coming along…
I hope this has been helpful!
Laz