Thanks. Based on our Slack discussion the problem is that Gnuplot depends on DataStructures = "^0.17" while OrdinaryDiffEq depends on DataStructures = "0.18".
Although I was under the impression that ^0.17 means anything 0.17 and above but not 1.0 since it changes the left most digit. This is not true. ^0.17 means anything 0.17.x but not 0.18.