There is an error in the button to apply changes, how to solve the issue?

Question

Asterisk

The button to apply changes constantly weighs, when you click on the button, an error occurs:
There was an error during reload: Unknown Error. Please Run: fwconsole reload --verbose
Unknown Error. Please Run: fwconsole reload --verbose
running fwconsole reload --verbose
shows :
Unable to find BMO Voicemail FreePBX class A required module may be disabled
or not installed. Recommended steps: (run from command
line): 1) fwconsole ma install voicemail 2) fwconsole ma enable voicemail

how to solve this situation?