Awhile back I missed a week or two in profession knowledge. I got weak aura that now says i am behind 9 points in alchemy and 5 points in engineering.
The thing is - I literally have done everything daily for a month now and have STILL not been able to catch up.
Why is this? You miss a spark, you catch up instantly. You miss knowledge points - you’re permanently behind.
What am I doing wrong - please advise.
Based on what I am experiencing on my professions, that close to catching up you should be seeing Work Orders awarding one, maybe two, Flickers per week per profession.
If you are not seeing those Work Orders, then the game system does not agree that you are behind no matter what the weak aura says.
The only crafting profession that can be fully caught up is enchanting. The rest, the closest I got is 1 point behind in engy. And I too do my best to fill in those patrons WOs with KPs items. So you are not alone.
The “catch up” kind of relies in getting lucky with what crafting orders spawn for you. If you were fully caught up, those orders wouldn’t spawn at all. As long as you are behind they keep spawning, but only 1-2 a day, so the catchup process is very slow.
I get 3 flicker patron orders for tailoring and alchemy each every day after reset no matter how far behind my alt is, I think that’s the “catch up” mechanic. if so it’s contingent on logging in each and every day which isn’t the friendliest. 
“Catch Up” is misleading, there is no catching up among the crafting professions. The patron system will only allow so many work orders per week and it’s a crap shoot at what you are getting. I get a lot requests for recipes I don’t have or recipes in trees I didn’t spec in, also some specs you have to be rich to be able do the a good number of the patron orders, blacksmithing, engineering and jewelcrafting. Gathering professions can probably catch up in a solid weekend, with the exception of skinning maybe.
There is catchup. The single KP craft orders will only spawn if you are behind in points.