I am using the Olympus EM1 Mark II and Lightroom 6.3. I have updated Lightroom and also tried to download the ACR 9.8 file from Adobe. It still won't regonize my Raw format when trying to import files.
Update Lightroom to 6.8
You have to update to LR 6.8, but it's only a preliminary support. It isn't completely tested. So you can still run in problems.
As advised by John and Axel proceed to update to Lightroom 6.8.
Lightroom 6.8 has its own raw processing engine and is the equivalent of ACR 9.8.
You do not have to uninstall your existing version of Lightroom just run the update (patch) package LR 6.8.