Sometimes my premade Sims can't use their powers/weaknesses?

This is because you have to take 45 weaknesses, according to this picture. If you have weakness points that you don't "spend" you're not allowed to save. 

Since some weaknesses conflict with powers, if you take certain powers you won't be able to take the conflicting weakness.  So having 45 weakness points that you're required to spend means that you would be unable to get Sun Resistance, Vampiric Slumber, Deadened Emotions, Tamed Thirst, and perhaps another one I'm forgetting at the moment. 

I would avoid loading up my vampire with 45 weakness points if I intended to use some of the conflicting powers.

Is there any way to fix this, or reset this? 

 (I tried putting in the weakness reset cheat/mccc center's reset weaknesses and it does nothing. the weakness reset cheat says that it's invalid.) 

I see what you mean...I wanted to make the father of a Vampire sim and I used a cheat to get him to grand master.. I hope there's a way to undo this!

@chocogotho  I honestly don't know if there's a way to reduce vampire weakness points!

You might be able to give them powers with command line cheats and not use the UI. There are a lot of lists of Vampire cheats around the internet;  one is here:  https://ultimatesimsguides.com/sims-4-vampire-cheats-2/

so i guess there is nobody that can help

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.72.28.1030
What expansions, game packs, and stuff packs do you have installed? all. laundry stuff pack, tiny living, cool kitchen.
Steps: How can we find the bug ourselves? Just go on the Vampire sim's powers and weaknesses.
What happens when the bug occurs? When I try to pick powers/weaknesses.
What do you expect to see? Nothing. Nothing works.
Have you installed any customization with the game, e.g. Custom Content or Mods? Yes
Did this issue appear after a specific patch or change you made to your system? No

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so, i wanted to make a premade vampire sim in cas (I made one sim as a vampire, and I wanted to make the parent of that vampire), and make him above the minor vampire rank. what i didn't know, is that it would totally mess up my "take weaknesses" thing, and now i can't select any powers or weaknesses at all! is there some way to reset the weaknesses completely where i don't have any at all? i tried everything, and with the limited vampire cheat system (because devs removed half of it, don't know why), and now my vampire is forever some dud that could only suck blood from people.