Meraki MX64W Firmware Version

[TomT7773]

I have an intermittent problem with a customer. They have problems with VoIP, what is the latest firmware for the MX64W 

[BeachBum]

The latest stable version for the MX is 14.39, the latest beta is 15.13.

In the Dashboard click on Organization and then Firmware upgrades, it has the info for all devices.

[BrandonS]

Just curious if the trouble is with wired or wireless connection or both?  I am troubleshooting a problem with RingCentral on iPhone and have discovered an issue with MR v26.  I am not sure if it could also be with MXW as well.