Trouble with lockpicking

Hey,
I´m having trouble with lockpicking on my rogue. I can only open some strongboxes (buccaneer´s strongbox is actually the only one I tried outside questing) and got my lockpicking to 100+. I still can´t open lockboxes, chests or anything. I´ve tried everything I could think of so I could properly utilize lockpicking, but nothing seems to help. Am I just dumb and I´m missing something or is there something wrong? I´ve never had this problem before and I´m kinda lost.

Thanks you for your help.

https://legacy-wow.com/wotlk-lockpicking-guide/ Use this as a basic guide.