Have you clicked on
"TOOLS" on the top bar? If so, can you then click on the
"Download Manager" from the drop-down box that appears and does the
"Download Manager" open? Yes/No???
Also you could try this...
Click on
"Edit" on the top bar >> then click
"Preferences" in the drop-down box.
Now in the window that appears, in the left pane there is a heading named
"Navagator". Expand it if it is not already. Click on
"Downloads". On the right side of the Window it will have a list titled
"When starting a download". Below it will have 3 choices, click/highlight the one that says
"Open the download manager".
Click the
"O.K." button at the bottom of the window and then close out your browser and restart the browser ( you may want to restart the computer also if it's that something of the browser is not unloading). After you restart the browser try to download something and see if the download manager opens for you.
I had this problem once or twice before and I think this worked... The first time
The second time I had to reinstall the browser. Reason may be due to the browser crashing on more than one occasion and it has become corrupted.