installation problem

[cecilia]

I am working on an iMac with OS Sierra (not High Sierra). Although purchased in 2011 the computer was built in 2009. I downloaded and installed GIMP but although it told me it had installed successfully and on launch the icon appears in the dock, it only shows for about five seconds and then vanishes. 

I'm keen to explore GIMP, and wonder if this situation has a remedy?

cecilia
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