Incorrect external monitor resolution detected, true resolution not available I have a BenQ EX3501R monitor connected by HDMI to my MacBook Pro, which is a Early 2015 model.

The issue being that OS X gets the resolutions completely wrong - the monitors native resolution is 3440x1440 but it switches it to 6720x3780!

Alt-clicking the 'Scaled' radio box does not list the correct resolution.

For further confusion, a Mid 2012 15' MacBook Pro connecting to the same monitor via the same HDMI cable works fine. The only notable difference is that one has a GeForce chip, where as mine is Intel Iris.

Both are running latest Mojave 10.14.1

any ideas of a way to proceed?
It might be the Monitor profile used by Mojave that needs repair.

Open the Color sync Utility in the Utility Folder



Verify you Monitor is showing correctly under devices.

Use the Profile First Aid.