Mastery ability not working

[lmaoball]

Currently level 20 Blackguard, I've put 6 mastery points into the "Path of Malice," 5 into climbing the mastery ranks and put 1 into the actual ability of "Enraged Beating." Now, it never appeared in my abilities tab. I kept questing and eventually ran into the RVR area in Shadowlands. It bumps your rank up to 48 and the ability appeared in my hotbar, along with the fact that I could use said ability. Eventually I left to continue questing, but the ability is no longer usable. When i attempt to use it, it says something along the lines of "your level is not high enough." Wondering what this is all about. Thanks

[BluIzLucky]

The level requirement for Enraged Beating is 21, you can probably get it to work when you get bolster in PvP, but may need to drag it from the Ability menu.

[Bosli]

This problem only exists while you have +1 mastery from gear sets and just barely unlock a skill. It will work in pve too once you get an extra level and would be able to have it without the +1.