I also have the exact same problem.  In fact, when starting OMOptim, it took a considerable amount of time for OMOptim  to put the canvas on; once it was on, I looked in the Message Output ( under Log/MO) and found the message OMC not started.  Please start it again (menu OMC->restart).  I try Tools/OMC/start omc and just like the previous post, I get:


08:43:31] OMC not started. Please start it again (menu OMC->restart)
[08:57:34] OMC: unable to find OMC server, Object reference file C:/Users/Daniel/AppData/Local/Temp/OpenModelica/OMOptim//openmodelica.objid.OMOptim{E5F24F12-CB25-40B3-81BD-255279DBC379}085713394 not created.

Anyone can help?  Thank you in advance.