I think I know what is wrong, and It’s my fault for not remembering to tell you this. It looks like you’ve done everything correctly up through creating the kit with the new name in your kits folder on your hard drive.
At this step, I generally quit BB Manager, and when I am asked if I want to save the changes I have made, I select “No.” This keeps the kit you altered with its original name, in your case, NP Rock 02 WG Bass 60-91. Otherwise, if you have selected “yes” to keep the changes, your original kit is named NP Rock 02 WG Bass 60-91 in the list of kits, but its name will be NP Rock 04 WG Bass 60-91 in the box under “Drumset Maker.”
To correct the problem from your current state, Start BB Manager, and select the NP Rock 02 WG Bass 60-91 for editing in Drumset Maker. Check the title under the Drumset Maker box. If it is currently NP Rock 04 WG Bass 60-91 you will need to first change it to NP Rock 02 WG Bass 60-91, then do Drumsets>Save Drumset. This will get the old name stored properly into BB Manager. After that, import the NP Rock 04 WG Bass 60-91, from your hard drive.
Then, you should see the NP Rock 04 WG Bass 60-91 at the bottom of your drum kits list. Select the kit to make it active, and then double click its name to open it for editing. This time, when you are asked if you want to keep the changes to your project, select “yes.” After that, the new kit should open and be ready for editing.