VoiceMail Directory

When I enter the mailbox to listen to the recored message I press "1"
and when the message starts playing all it plays is:
“First messge received” and silence.

The error message I get:

== Parsing ‘/var/spool/asterisk/voicemail/druid-default/2015/INBOX/msg0000.txt’: Found
– <SIP/phone-grandstream-83-088717c8> Playing ‘vm-received’ (language ‘en’)
– <SIP/phone-grandstream-83-088717c8> Playing ‘digits/yesterday’ (language ‘en’)
[Sep 22 08:56:11] WARNING[4347]: file.c:655 ast_openstream_full: File digits/at does not exist in any format
[Sep 22 08:56:11] WARNING[4347]: file.c:945 ast_streamfile: Unable to open digits/at (format 0x8 (alaw)): No such file or directory
[Sep 22 08:56:11] WARNING[4347]: say.c:414 wait_file: Unable to play message digits/at

Can soemone please help me.