It appears that NPM currently does not see the interfaces on the on the Cisco MX64w device. Cisco may have already done some of the work (see attached).
To add MIBs to the database, please refer to: https://support.solarwinds.com/SuccessCenter/s/article/Add-MIBs-to-the-SolarWinds-MIB-database?language=en_US