I have tried this in three Windows 7 virtual machines (all pretty much the same) and it always reverts to PLC v1.0 when DmSim 2.5 is reopened. Set the clock, accept the config, write or load a program, run it OK. Exit DmSim after disconnecting or just closing DmD and it is all gone.
One of these VMs already had v2.1 and it works as it should. I can even start the 2.1 sim and connect with DmD 2.5 and everything is great. Stop DmD and then exit the sim. Start DmSim 2.1 up from the start menu and it is still chugging away flashing Y1 like I told it to do. You can see the two behaviors without DmD running from the still in run mode on "power up" and the flashing LED of 2.1 to zip-squat in 2.5.
Win 10 DMSim 2.5 works as it should. What am I missing?
And no, I haven't played with any DmD configurations, registries, nothing, in two of these VMs, just fresh installs.