If the add-in is not disabled, then please check the following.
1) go to the manage add-ins and select teh REMSCore.dll add-in. In the description does it indicate that any error has occured?
2) If you right click on your toolbar area you should get a list of toolbars, is it listed and not checked?
3) If you go to teh list of add-ins (from step one) do you see REMSCore at all?