We have got hold of Nexbox MXQ Pro android TV firmware and it will help you factory reset it and delete all data allowing you to start afresh. Download firmware from here and flash it using this method.
Decoder Format: HD MPEG1/2/4,H.264,H.265,HD AVC/VC-1,RealVideo8/9/10,RM/RMVB,Xvid/DivX3/4/5/6
Video format: 3D,4K x 2K,AVI,DAT,FLV,ISO,MKV,MOV,MPEG,MPG,RM,RMVB,TS,VOB,WMV
Audio format: AAC,AC3,APE,DDP,DTS,FLAC,HD,MP3,OGG,TrueHD,WAV,WMA
Package Contents: 1 x NEXBOX MXQ PRO TV Box, 1 x Power Adapter (5V 2A), 1 x Remote Control, 1 x HDMI Cable, 1 x English User Manual
* CPU: Amlogic S905 Quad core Cortex A53 2.0GHz 64bit
* GPU: 5-core Mali-450MP GPU
* 1GB DDR3 RAM
* 8GB Flash ROM
* USB 2.0 * 4
* USB disk and USB HDD supported
* Card reader: SD / SDHC / MMC cards
* Support the latest HEVC (H.265) decoding
* Support 4K*2K Super HD video
* OS: Android 5.1
* Wifi: IEEE 802.11b / g / n, 2.4G / 5G, the fastest wireless internet
* Wired / wireless mouse / keyboard supported