REF! error when referencing another worksheet

Hello,

I am trying to reference cells in two other worksheets, for just a simple subtraction. In the picture I attached, I've typed in =MaterialsDist!b14-MaterialsRem!b15

I feel like this should work, but every time I hit enter the box pops up telling me to "update values," and prompting me to pick a file. I don't know why this is happening, or what I am supposed to pick. If I just hit cancel, I get the !Ref error.

(FYI The tabs previously had different names, with spaces in them. I right-clicked to rename them with no spaces. I also resaved the whole workbook under a different name with no spaces. I'm not sure if that makes a difference.)

Thanks!

update values: worksheet

Kalibasa said:

every time I hit enter the box pops up telling me to "update values," and prompting me to pick a file.

Click to expand...

Try or look here or here