Custom audio files don't work anymore

Hi,
after some time my IVR doesn’t work anymore.
When I call I don’t listen anything, it’s mute. Checking the log I found this:

[2015-05-22 19:02:47] WARNING[6161] file.c: File custom/ivr_rec_ok does not exist in any format
[2015-05-22 19:02:47] WARNING[6161] file.c: Unable to open custom/ivr_rec_ok (format 0x8 (alaw)): No such file or directory
[2015-05-22 19:02:47] WARNING[6161] pbx.c: ast_streamfile failed on SIP/SIP-0xxxxxxx-00000005 for custom/ivr_rec_ok
[2015-05-22 19:02:52] WARNING[6161] file.c: File no-valid-responce-pls-try-again does not exist in any format
[2015-05-22 19:02:52] WARNING[6161] file.c: Unable to open no-valid-responce-pls-try-again (format 0x8 (alaw)): No such file or directory
[2015-05-22 19:02:52] WARNING[6161] pbx.c: ast_streamfile failed on SIP/SIP-0xxxxxx-00000005 for no-valid-responce-pls-try-again