Well, no the browning ship has already sailed. But you can cook it longer and get it tender. Searing it would have locked in some of the juices, but that may not even be why it's tough. Could be the cut of meat, could be the particular animal it's from, could be lots of things. But what I would do is add some onion and spices (if you haven't already), place it in a baking pan like glass with lid or foil, add some water and cook it in the oven. I would cook it at about 300 degrees (F) for a couple hours, minimum. The longer beef cooks (as long as there is some moisture there, so keep adding water if it cooks away!) the more tender it will get. I don't know about eating it right away though.
Other options are to shred it up and use it as pulled beef. It still won't be too tender, but it'll be easier to chew. You can shred it up and add barbeque sauce to it, and make pulled beef sandwiches. Letting it simmer for awhile in the sauce will help a lot too.
Or you could cut it into small cubes, then boil it on the stovetop for a couple of hours, with some beef bouillon and it will get tender. You could use it in soup, beef pot pie, and so on.
Shellee, firstly to answer your question, no. What is troubling me though is why is your meat tough. I have cooked beef shoulder, which is a very tough cut of meat, and I have never had it come out tough.
The answer must lay with you, there has to be something you missed doing or adding, and I do not mean the browning.
As another answerer stated, browning will only makes the meat look better, it will not tenderize a tough piece of meat. You probably did not cook it long enough. You can slice up the meat, put the meat and the sauce in pot with a cover and simmer on top of the stove until it gets tender. If you have no sauce or gravy from the crock pot, use some low salt beef broth. I usually make my pot roast in the oven the day before I plan on serving it. If it is tough when I cut it up, the day after cooking it, I just simmer it on the stove top for 30 minutes or so and it gets really tender.