Extensions limit

Hello fellows,
I’m new with Asterisk. I have a problem when I add an extension. for example 60800. this one can make calls, but can’t recieve(busy tone)
I think that there is a restriction , that doesen’t let me add any new extension.
do you have any idea?
thanks a lot. excuse me for my english, it’s not my native languaje

Have you tried the extension from another phone? Are you sure it is registering correctly?

There are no restrictions. It would be very difficult to maintain a nobbled open source version.

hello, I register the extension in a softphone, in a IP phone and the error is the same.
the problem is not with just one extension, is with all the extensions I add to sip.conf and extensions.conf

here is the code, but I think that this is not the problem.

[60800]
deny=0.0.0.0/0.0.0.0
disallow=all
type=friend
secret=60800
qualify=yes
port=5060
pickupgroup=
permit=0.0.0.0/0.0.0.0
nat=yes
mailbox=60800@device
host=dynamic
dtmfmode=rfc2833
dial=SIP/60800
context=fullaccesspin
canreinvite=no
callgroup=
callerid=device <60800>
allow=ulaw
allow=alaw
allow=gsm
call-limit=50

Are you editing the file manually or do you use FreePBX or any distributed packages?

I edit the files manually. but I copy/paste the code from a other extension, and change the number.
thanks