If set to Attackable NPCs continue to ignore damage. But, you can inflict damage by throwing a trident or shooting a bow.

Thanks for the details. Unfortunately I'm unable to reproduce the issue on 1.20.1. :(

It seems it's related to one of your used mods.

Try if the same happens, if you save and reload the world ?
Could you also share the used mod pack or a list of mods you are using in this case ?

I'm currently working on enable attackable without a respawn, maybe this will solve your specific issue as well.

Please try to use the "respawn" button, because in some cases a "respawn" is need to make sure the updated settings are used.

Furthermore the issue with the throwing a trident or shooting a bow is fixed in the latest version.
If you still have issue, please share more details like the used version and the exported NPC with the issue.

Thanks for the quick reply. I did everything you asked. The problem could not be fixed. I have recorded a detailed video for you. The exported NPC is also included :)

https://youtu.be/lPVZHOmvLoc

NPC.zip

I currently running some troubleshooting with Project MMO, did you have by any change this mod installed ?
It seems with this mod installed, regardless of the attribute you can not damage the NPCs.

Hi. No, I didn't install Project MMO.

I want to try to rebuild my modpack. And if the problem is not fixed, I will upload my modpack. So you can check it out for yourself.

I uploaded a new version 3.11.x which includes some fixes for some mods including Better Combat.
Please let me know if this fixes your issue, if not please share the modpack for further testing with me.
Thanks.

Yes, it's working! Thank you very much for your help. Version 3.11 works as it should. Still need to press the "Respawn" button to enable "Atackable" but that's not a problem.

Thank you very much again for your help!