Hint:MWI ... help, I am not able to make it works

I’d like to use a normal BLF key for monitoring voicemail, so I entered in extensions.conf the following entries:

exten => *98104,hint,MWI:104@DEVEL
exten => *98105,hint,MWI:105@DEVEL

And they are correctly read by asterisk (core show hints)

*98105@authenticated: MWI:105@DEVEL State:Unavailable Presence:not_set Watchers 0
*98104@authenticated: MWI:104@DEVEL State:Unavailable Presence:not_set Watchers 1

Unfortunately, it seems asterisk is not checking if there is any voicemail for 105 or 104 in the DEVEL context. I am using ODBC as storage engine for Voicemail and I have set pollmailboxes=yes and pollfreq=30. I have also tried leaving a message… MWI for voicemail 104@DEVEL when subscribed by the phone is working, but not when used with the MWI hint type.

Where is my mistake?