Each time I try compute a head model, I continually receive an error message saying OpenMEEG is not downloaded or needs to be updated. I have tried downloading and unzipping the file from the website, changing the location of the folder, and trying to update and install within the Brainstorm software, and have come back with nothing. Each time I opt to update the software, it goes through the downloading process as if everything is being configured, but each time I return to the data set to compute a head model, it will give me the same "not downloaded/updated" error message.
I think I fixed this bug with this commit: https://github.com/brainstorm-tools/brainstorm3/commit/71810dc618b52be4c349bd9fd03fd28329f58f84
I'm suprised no one reported this issue before...
Please update Brainstorm, try again and let us know if the problem is gone.