What version of Excel are you using?
I suggest that you update your Account details (or click your user name at the top right of the forum) so helpers always know what Excel version(s) & platform(s) you are using as the best solution often varies by version. (Don’t forget to scroll down & ‘Save’)
Can you post some sample data to the board.
MrExcel has a tool called “XL2BB” that lets you post samples of your data that will allow us to copy/paste it to our Excel spreadsheets, so we can work with the same copy of data that you are. Instructions on using this tool can be found here: XL2BB Add-in
Note that there is also a "Test Here” forum on this board. This is a place where you can test using this tool (or any other posting techniques that you want to test) before trying to use those tools in your actual posts.
I found that if I select the range of dates and use Text to Columns, it will quickly convert them all.
I'm now seeing two "odd" things going on.
1 - When I look at the formula at I$ in the formula bar, it is black as usual. But, J-T4 are more grayed. Plus, I can't take the formula beyond 12/18/2021, even though there are definitely dates beyond that.
2 - Only the sumifs formula at I5 is showing an amount. I tried to make the references absolute with $, and it doesn't help.