Hi Muhammad,
It seems to be some config issue to me.Since the config is not avilable, just have a look at this sample config.
aaa new-model
!
!
aaa authentication ppp default group radius
aaa authorization network default group radius
aaa accounting network default start-stop group radius
radius-server host X.X.X.X auth-port 1812 acct-port 1812
radius-server key testradius
If the device you are testing is a test device, try to make the changes and share the results.
If still face the issuem, collect the following debugs:-
debug aaa authentication
debug aaa authorization
debug radius
thanks,
Vinay
Thanks & Regards