21:9 (2560x1080) ultrawide monitor Macbook Air doesn't work after macOS Sierra
I'm having trouble with my LG 29UM58-P.
After installing macOS Sierra, Switchresx (4.5.3) doesn't have my custom resolution 2560x1080 anymore. I already tried to uninstall Switchresx and made new custom resolutions but it didn't help... First it didn't save my custom resolutions and then it said 'not installed' or 'not activated - invalid?'. Someone also said if you made an extra account on your mac and then set the custom resolutions, you could then use it in your normal macaccount but it also didn't work..
I tried (almost) everything.. before the software update it did work just fine. Oh and also I'm using HDMI to a mini displayport.
Could anyone help me out here?
Thanks a lot !
MacBook Air (13-inch, Early 2014), macOS Sierra (10.12)