Fabric Version 1.20.1 ,v1.56.0 (happened on v1.55.0 also)

If someone has the Greater Momentum power on a runic weapon, it cannot be activated until someone (either yourself, or someone else if on multiplayer) uses normal Momentum. The ability works fine after this (until the server/world is reloaded, where the same issue appears again.)

Fixed in the 1.21 pre-release versions