I had the same problem till I realized, the issue was the MacBook couldn't detect the correct refresh rate for the monitor and was using an unsupported value even though the existence of the monitor was detected. Going to display settings and changing the refresh rate in my case from 144Hz to 120Hz fixed the issue.
My setup had two exact same monitors, one connected via a HDMI to USBC cable and another connected via an HDMI->HDMI->USB-C adapter. It only detected the correct refresh rate for the latter. The first screen showed up in arrange displays but the screen wasn't working.
pintojoey
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