NPC Spell Attack Modifier not calculated correctly

Hi folks, I've been tinkering with this for a good while and haven't been able to solve it. I have a NPC in my Dragon Heist game that should have a +15 to hit with his spell attacks, and a spell save DC of 21 - as per the Dragon Heist module. However, when I have him attack with say, a Fire Bolt, the roll only adds +9. I've tried to add a global magic attack modifier and I've tried clearing the CR of the NPC (a suggestion I came across via a google search) but still nothing is working on my side. I've even tried directly changing Fire Bolt to use the NPC's strength modifier just to get a different result and it still defaults to +9. Would love to get some advice! I've included an image of the NPC's sheet below.

Have you moused over the roll to see what it's actually rolling? It should be adding spellcasting ability mod, proficiency bonus, and the Global Magic Attack Modifier. So the tooltip should look something like this: 1d20cs20 + 5[INT] + 7[PROF] + 3[SPELLATK] The proficiency bonus is calculated from the CR of the creature (I think). What exactly is being added to the roll for this NPC? Are you using Firebolt from the Spells section or the NPC Actions section?

Aside from the good questions Oosh is asking, you will want to set the following fields based on equipment in the stat block: Global magic attack modifier: 4 Spell Save DC Mod: 2 Challenge must be filled out for the attack bonus and save DC to be calculated properly. Even then, with just the default +2 for a CR 0 creature, the stat block should then give a +12. A CR 13 to 16 would give +15 to hit for spells.

Thanks Oosh and Brian C. for the replies! Good call on the mouse-over. For some reason its got the NPC's proficiency bonus at 3.No spell attack modifier is added regardless of what number I have in there. Attached below. The CR is currently not filled, but I just tried changing it to 16 with no change. I'm also trying to cast Fire Bolt from the NPC's spell section of his sheet. I've also tried opening the game in Chrome and Firefox to see if there was any change there but nothing was altered.

Are you creating the spell from scratch or dragging from the compendium? If you have not already, try dragging from the compendium, otherwise, show us the settings for the spell ("i" to expand, cog to show settings).

Thanks for the reply, Brian C. This was preloaded on the NPC's sheet as I bought the Dragon Heist module from roll20. Interestingly, when I tried to alter another NPC spellcaster's sheet, it responded correctly to any changes to the spell modifier value. I may have to simply rebuild that first NPC's sheet... not sure why its always giving back that +9 value. I attempted to drag a different cantrip (Ray of Frost) from the compendium, and upon clicking that it simply returned 'blank' entries into roll20 chat. Attached below is the Fire Bolt settings as requested!

"Blank" chat output? That sounds like it is messed up for some reason. I would suggest recreating the NPC. If it works, then re-link the token.

Thanks, Brian! I'll give that a shot!