The Grunt tries to work out how many TUFLOW models might already be running on the computer even if they are not being managed by TRIM. For example, if that computer had a 4 local dongle but was already running 2 simulations, it would then only allow TRIM to start 2 more simulations on that Grunt even though your Max Sims might be 4. I hope this makes sense.
Unfortunately, it can get confused. It works by looking for the word 'TUFLOW' in the Window captions. As such, if you have other windows open with TUFLOW in the name, the Grunt may mistake them for running simulations. Examples may include Windows Explorer open with a path that includes TUFLOW or a Word document open that includes the word TUFLOW in the title. If you close down any windows that might confuse it, hopefully it will get the running simulations count correct.
Grunts work best on dedicated modelling computers with few or no other applications running.
Please let me know if this helps.