Most of the singularities (likely the one for the elements) are missing

Any ideas on what is wrong or how to fix it, or is it a bug?

thank you that has fixed it

Sounds like the CraftTweaker scripts didn't run properly. Where did you download the pack from?

It was downloaded from the curseforge installer

I also just uninstalled and reinstalled the pack and the problem persisted

Check your 'singularities.cfg' file with a text editor and verify that the elemental singularities exist there. Also, check the date that file was last modified.