I updated my Mac OS to Mojave (10.14.1) on one of  my computers to test various Apps, and MRIcroGL is one that doesn't work as it should.  A background and overlay image is loaded, but only a partial image.  Has anyone got a quick fix in settings for this?  Best wishes, Lucy Brown

Are you running version 1.0.20180623? If not, I would suggest getting that version. I would try holding the shift key down when you launch the program - choose to reset evrything - the first time I would choose the default options each time (as these give the best performance but expect the best hardware). If your issue persists,  you could check the troubleshooting advice.

It turns out that I was just looking at the default background brain that came up when I started the program and I assumed it was an MNI template.  When I actively opened one of the MNI files, and other templates available, they loaded fine, as did overlays.  So, there is no problem!

I've just installed the security update 2018-002 for 10.13.6. dcm2niix had been working on my machine but no longer seems to be. When I either use the drag and drop or clicking through File>DICOM to NIfTI, the gui isn't running hte conversion.

Be aware that when you upgrade MacOS it can apply Gatekeeper Path Randomization - this is intended to block mal-ware, but it can also confuse legitimate tools that expect executables to be in a specific path. Can you first check that you are using the latest version (v1.0.20180623). Next, I would try reinstalling the latest version: https://github.com/neurolabusc/MRIcroGL/releases 

Hopefully, this will resolve the issue. It is hard for a developer to solve, as Apple is intentionally making the path of executables hard to predict, using randomized folders that are hidden from the user.