#DIV/0! error where there was none before

A worksheet of mine is returning tons of #DIV/0! errors where it should not. It was fine for weeks before, and today I just noticed it is wigging out, even though I can't think of anything I have changed on the sheet it pulls data from. I know I definitely havent changed anything in the formulas.

The sheet pulls data from another sheet in the excel file:

=SUM(IF('NBA Line Watching'!M31:'NBA Line Watching'!M9999="ATL",IF('NBA Line Watching'!O31:'NBA Line Watching'!O9999="W-b",1,0)))+SUM(IF('NBA Line Watching'!M31:'NBA Line Watching'!M9999="ATL",IF('NBA Line Watching'!O31:'NBA Line Watching'!O9999="W-bi",1,0)))+SUM(IF('NBA Line Watching'!M31:'NBA Line Watching'!M9999="ATL",IF('NBA Line Watching'!O31:'NBA Line Watching'!O9999="W",1,0)))+SUM(IF('NBA Line Watching'!M31:'NBA Line Watching'!M9999="ATL",IF('NBA Line Watching'!O31:'NBA Line Watching'!O9999="W-i",1,0)))

The other sheet is called NBA Line Watching.
What I'm doing here is going through and looking for every game played by ATL (column M) in which a W-b, W-bi, W, or W-i appears in column O. Rows are from 31 to 9999.
I started getting DIV/0 on one part of this sheet where I use these formulas, but on the other part of the sheet with very similar formulas I have NO problems. Here is that formula:

=SUM(IF('NBA Line Watching'!K31:'NBA Line Watching'!K9999="ATL",IF('NBA Line Watching'!L31:'NBA Line Watching'!L9999="W-b",1,0)))+SUM(IF('NBA Line Watching'!K31:'NBA Line Watching'!K9999="ATL",IF('NBA Line Watching'!L31:'NBA Line Watching'!L9999="W-bi",1,0)))

Here I'm pulling ATL from Column K when there is a W-b or W-bi in column L. Working fine.

None of the referenced cells in the troubled formula have been moved or altered or anything. This stuff was literally working fine one day (for a long time) and broken the next. I tried hitting F2 and then CTRL SH ENTER and no luck.

Any help is appreciated, thanks!

Carefully check through columns M and O... there must be a #DIV/0 error somewhere in those columns....especially where there might have been a match...

BTW: you don't need to repeat the sheet name for the top and bottom of each range.... this'll shorten the formula a bit:

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or even shorter and better...you can use sumproduct and you don't need to confirm with CTRL+SHIFT+ENTER. Just ENTER will suffice:

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Still better and shorter and easier to add more conditions is to add an Isnumber(Match()) check....

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