Data Validation ComboBox Error

Hello,

I've made a data validation combobox with the code provided by Contextures, and it was working at one point but now it has stopped and I honestly don't know why. I don't get an "error" box per say, but what is supposed to happen is that double-clicking on the data validation cell should open up the combobox where I can type in a "product number", but now nothing happens at all. I'm a little frustrated because this would happen a lot before and somehow (by just guessing, playing around, and luck) I got it settled in. No it just started up again and I'd like to understand why instead of going through the usual days of playing around with it. If it helps, the last "major" thing I remember doing is changing the value of the cells in the first column of my data table to text format from number. However, I don't know when it was exactly that it stopped working. I'm attaching a sample workbook to further explain my situation. I need to be able to keep the values from the table in Text format, so any help would be appreciated in that. I haven't done anything to change the code (it is as it was in Contextures, except I changed the Sheet name and ComboBox name to suit mine).

Thanks for all your help in advance!