Hi Chris thank you for your prompt reply, it seems that it is looking for AfniDir. I don't have AFNI in this machine and have never defined a path for it. Please find it below the result from the terminal:

~$sw_vers
ProductName: macOS
ProductVersion: 11.6
BuildVersion: 20G165
~$
~$locale
LANG="en_AU.UTF-8"
LC_COLLATE="en_AU.UTF-8"
LC_CTYPE="en_AU.UTF-8"
LC_MESSAGES="en_AU.UTF-8"
LC_MONETARY="en_AU.UTF-8"
LC_NUMERIC="en_AU.UTF-8"
LC_TIME="en_AU.UTF-8"
LC_ALL=
~$
~$/Applications/MRIcroGL.app/Contents/MacOS/MRIcroGL
Searching for AfniDir
Terminated: 15
~$
~$/Applications/MRIcroGL.app/Contents/MacOS/MRIcroGL -R
Searching for AfniDir

At this stage, the app continues to search using 99% resources of one core until I terminate it. I tried uninstalling the app and deleting the MRIcroGL .ini file stored in ~/Library/Application Support/MRIcroGL/ and installing the app again but did not work.