Eldritch Blast NaN error

My player who is a multiclassed warlock is getting the following error when casting eldritch blast: Any idea why the NaN is happening? The rolls are definitely not calculating correctly. i'm using the 5e OGL

Go to the spell's roll settings in the Core tab under Attacks & Spellcasting. Right at the top should be an Attack checkbox, checked, followed by a couple of options. "SPELL" should be selected in the next drop-down - try changing this to something else, then back to "SPELL". If that doesn't fix it, check the Spells tab of the sheet. What's in the top-right for "spellcasting ability" and "spell attack bonus"?

"NONE" and 0. I changed EB from spell to charisma then back and nothing. I also manually set the spellcasting class to cha and it still did nothing...

What's the multiclass, out of interest? If it's not a CHA based class, you'll want to manually set the spells to the correct stat, instead of using SPELL. When you change the spellcasting class to CHA on the Spells tab, do the DC and Attack Bonus fields update correctly?

They do not, unfortunately. He's multiclassing from rogue.

Cast the spell, go into the chat box and press the up arrow. This should show exactly what was sent to chat and might give a clue as to where the number is coming from.

It appears that the NaN error is not an issue any longer, which is very strange because I haven't done anything to resolve it. I figured out how to change the spellcasting stat on the character sheet, but I'm unable to change the Spell DC/ attack bonus: Any ideas how I can fix this?

Changing the Spellcasting Ability should be triggering the sheetworker to calculate those 2 stats.... and it's mathematically impossible for them to both be 0. So clearly something is messed up. Try changing the character name first, something simple and something that definitely doesn't already exist in that game, and has never existed in that game. Then try changing the Spellcasting Ability again and see if the sheetworker calculates those other stats. Sometimes you'll get ghost duplicates of sheets, and sheetworkers and macros keep targeting the wrong one. If the name change works, you might have a duplicate of the sheet somewhere in the Journal that's messing everything up. Export a copy of the character before you go deleting the duplicate - sometimes it will remove both. See if that gets you anywhere.

Changing the name and removing/re adding the spellcasting modifier worked! Thanks everyone!!