Question: unable to evaluate the function to numeric values in the region

ygraph1 := -.736312023696564122*exp(2.26140104440167664*10^5*tt)-.591826613918776445*exp(28994.5376895644186*tt)+.328002839648234568*o*exp(13767.7178702679158*tt);
ygraph2 := -.591859486202007235*exp(2.26140104440167664*10^5*tt)+.328381376616263988*exp(28994.5376895644186*tt)-.736116852194203974*o*exp(13767.7178702679158*tt);
ygraph3 := -.327943520064913564*exp(2.26140104440167664*10^5*tt)+.736143281263262450*exp(28994.5376895644186*tt)+.592069351595225779*o*exp(13767.7178702679158*tt);
FunctionAdvisor(branch_points, ygraph1);
plot(ygraph1, tt=-5..5);
plot(ygraph2, tt=-5..5);
plot(ygraph3, tt=-5..5);
Warning, unable to evaluate the function to numeric values in the region;
 
how to plot this system?
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