Thank you for your tests. [:)]

(1) It doesn't work correctly with the sh3d.jnlp version. First time I tried it asked for a browser location, the second time it dodn't work at all.

This plug-in can't work with Java Web Start (JNLP) version of Sweet Home 3D. Normally, a message explaining this is supposed to appear, but I forgot to test that. I fixed it.

(2) it seems you changed something in the coding of the Export to OBJ format routine.

This bug already existed when you exported/imported manually (this new plug-in just automates this process).
It's the same bug as the one Yafeng reported.