Custom destination not working: sent to invalid extension but no invalid handler: context,exten,priority

I’m trying to create a custom destination that receives a 6 digits number, then makes an HTTP request to mi API and says whether or not the code is correct.

This are the lines in extension_custom.conf:
exten => 20,1,Answer
exten => 20,n,Read(get,“silence/1”,6)
exten => 20,n,SayDigits(${get})
exten => 20,n,Set(foo=${CURL(MY_URL,code=${get})})
exten => 20,n,SayDigits(${foo})
exten => 20,n,Hangup

The custom destination has this target: custom-checkin,20,1

When i try to call the custom destination the call ends.

I found this error in the asterisk log files:

[2017-09-14 18:48:47] WARNING[21610][C-00000002] pbx.c: Channel ‘SIP/messagenet-00000000’ sent to invalid extension but no invalid handler: context,exten,priority=custom-checkin,20,1

Can anyone help me?

Is this a typo? The file is extensions_custom.conf.