For your FindRow() formula, you'll want to specify the column for the order ID from the input row. So you would put something like $[InputRow][Column Name of Order ID].
$[InputRow] by itself would have the data of entire rowlink rather than only the specified column.
Also from looking at your screenshot, I can see how the the automation field evaluating correctly would be confusing. I'm in touch with the team about this, since an error or warning should show instead.
If you click on the data cell where the "1" is, you can see in the Properties under the "Data" tab what the data source is of that variable (which likely will be the column name that is storing the order ID).
Then in your formula, you can plug in $[InputRow][Column Name of Order ID].
From looking at your screen, it could possibly be $[InputRow][OrderID], however you would want to confirm the name of the column either by clicking the variable or looking at the table itself.
I was able to figure out a workaround. Instead of trying to recover the field value with a findrow against the table, I was able to get the value directly from the $InputRow.
I think the reason it didn't work initially is because the source to the block with the button wasn't set.
Thank you for sharing it here as well, in how you adjusted the data source of the block.
I'm working with the team to address the formula validation issue we bumped into during this (with the formulas evaluating correctly but not returning desired results upon execution), since it can cause confusion when writing the formulas in the automation fields.
Feel free to reach out again if you run into anything else or have any questions.