Blank Monitor Nothing Shows Up

my libre renegade works with a tv but when i use a portable monitor, it is blank.any way to resolve this issue?it worked before but after a few reinstalls/sd cards, it no longer works.maybe a driver or code needed to allow other monitors. it is a spectre J20. it acts as if no signal is sent to the monitor but no issues with a tv i use as a backup monitor.

The Spectre J20 uses an odd resolution (1600x900) which may not be supported by the upstream clock generator to drive such a resolution. We recommend standard resolutions such as 1080P, QHD, and 4K for now.