So… as i saw here in this forum that this isn’t a new bug, but anyway, just repporting as well.
I was on my alt sharpshooter and used a stack of 10+ green engraving books. They didn’t add any “points” to my loyal companion engraving at all (so i lost 10+ green books?).
After that, any green book that i try to use comes with the error message described in the title of this topic.
i’ve tried the other topics solutions but it did not worked on my alt.
I hope that the devs fix this soon, i just lost my will to play with this alt now and if this happened on my main it would be the end.