Question: GNU compiler error ? Maple 2021

Dear Sirs, 
I was with my students today, and attempting to do a Math Maple exercise. The assignment contained the requirement to plot three graphs in one plot f,g,h. Those with windows pc and maple were able use the proper command. 

plot({f(x),g(x),h(x)}) or plot([f(x),g(x),h(x)])  however some of those with MacOS would inside Maple 2021 get an error which said "GNU compiler not found", when using the same command. For those there was no other way (that I knew off) than to do a 

p1:=plot(f(x)): 

p2:=plot(g(x)): 

p3:=plot(h(x)):

and then plots:-display([f(x),g(x),h(x)]):  which work.

But why the MacOS error ? Any idea?

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