I have installed both OpenOffice 4.1.3, LibreOffice 126.96.36.199
and LT 3.7 on both. The behavior is the same.
The basic problem seems to be that when I try to
do a LT grammer check by choosing
OO and LO both start their OO or LO grammar check pop-up
rather than the LT pop-up.
I tried reinstalling LanguageTool-3.7.oxt, reinstalling Java, and
the (often) sovereign cure of a reboot. These did not fix the
problem. Probably I should delete then reinstall everything
related to OpenOffice or LibreOffice.
Meanwhile, I have switched to using the browser/html version of LT. This
work well, although a pdf version would be even better since
my final output is in pdf.