Update: So far, with some help, it’s been discovered that the backslash characters were missing. I’ve revised the code to:

(\d+)?(\w+?.?\d+[:]\d+)(.\d+)?([,\d]+(.\d+)?)*

From here, I need to figure out how to add looking for Roman numerals, to cover instances of something like I Corinthians or II Corinthians. Then, how to include the next complete word after the reference, in case a translation is mentioned (e.g. ESV or NKJ).