Designer Mouse battery cover not closing

Place it the other way around, upside down and see if it works

Yes, the fix is fairly straightforward but it does involve taking the mouse apart.  I have since sold the mouse and I can't recall how I separated the upper and lower parts!!  I seem to remember using a flexible guitar plectrum.

Once opened, you will probably see a clump of tiny magnets stuck together.  There are a series of small depressions, where the magnets are intended to be sited, down either side of the battery aperture.  I simply reaffixed the magnets with a tiny dab of contact adhesive.

Et voila! :)

No, I think the OP has the same issue I have - the cover will not stay in place it just drops off the bottom of the mouse.

I imagine it should be magnetic?

i,ve got the same issue.

did you fix it ?

Is this what your mouse looks like from the bottom?

If the cover is not closing I'm just guessing that one or both batteries are not seated properly. Put the negative side in first, push it up and then in at the bottom. Sometimes rolling it in its slot helps me when I have difficulty but it should pop in.