I don't believe so. The flashing dot just indicates waiting for a command. If DISM.exe /Online /Cleanup-image /Restorehealth were running, you would see a % bar/line (see pic) indicating it is working and how far along it is. Mine just now took only about 5 mins, but it is a solid state drive. About 30-45min on a HDD...?
As to why it wouldn't be working at all, sorry I cannot help you. I do recall it not working or not being available on W7, but again I'm only going on my own experience here.
Also, make sure it is an "admin" cmd prompt. It will say - C:\WINDOWS\system32>, (as opposed to - C:\Users\Bill>)
I'm sorry I can't help with reasons why and how to solve it. I wish someone did know, or could help, as I am getting a wee bit tired of this same question so so many times. I will just have to unsub from this thread if nothing changes.
Good Luck!