Voicemail Not Coming in Until Days After Being Left

[Drew9213]

I'm running 3CX version 15 SP 4 on the latest update for one of my clients and they are experiencing a weird delay in their voicemail. Voicemails being left on their extensions are consistently not showing up in their email or on their phones until days later. For example, a voicemail was left for an extension on Friday morning last week (3/31/17), the phone did not display a voicemail until this morning (4/4/17) and the user did not receive an email notification until this morning. All extensions are set to email the voicemail as an attachment and leave the message on the extension as well.