my understanding is that people are having difficult, but not impossible times booking on Oman Air. Certainly much better experiences than the post above from 2 years ago, which i assume you are referencing.
I actually need to book 3, one way Oman Air tickets for Feb with EY miles...just haven't done it yet. The consensus seems to be that you should be able to find an agent to help now, but you may have to call back a couple times to find a capable one.