Sorak fight in the secret tunnel after the Outpost.
All of my spell casters, Ranger included, have at least one spell missing from their selectable spells during combat.
Moved ranger to height advantage and couldn't select Hunter's Mark because it didn't show in the options. Same with my wizard, I wanted to give a little extra light but couldn't select sparkle to light the sconces.
Both spells were in their proper places in the respective spell books, but not available to cast.
There might be a small oversight on my part, but it also stated that I couldn't cast Jump with my ranger because he didn't have a spell pouch. Checked my inventory, he doesn't have have a spell pouch but was able to cast jump yesterday during the initial combat getting into the Outpost.
Fight with honor, die with glory
Spells like Hunters Mark sometimes only appear as a bonus action when it is just being reapplied. That’s what I noticed in my games. Same with Sparkle when in combat.
Rangers need a holy symbol I think. I could be wrong though.
Spells that have casting time: bonus action, like Hunter's Mark, show up in the other spell casting dialog from the bonus action section when you're in combat.
There is also a potent Cleric healing spell called Prayer Of Healing that can only be cast outside of combat.
However, there is a 4th level Life Domain Cleric spell called Guardian of Faith that doesn't show up in any spell casting dialog... That looks like a bug.
make sure you dont have anything as a secondary weapon. if both hands are occupied you cannot cast spells and they will be grayed out. hope this helps