Any Admins have tips to get Billing Address to update via CSV import? Import says successful; but, it isn't updating. Tried using external ID and just text values.

Are you using the external ID of the Address record or the parent (customer or vendor) record? To update an existing address, you need to map both the parent record Int ID and address record Internal ID. I'd also check if your prior update attempt might have added a duplicate address record. That's usually what happens if you don't map the Address Internal ID. Not that I know from experience 😬

I assigned an external ID to the address record when i originally set it (learned that lesson the hard way too). However, I cant get it to update on the Sales Order.

Oh you're talking on a transaction. Are you referencing Bill-To Select in your mapping? You might need to. Maybe set that to custom and import the new address or select a new value in that field if the address you're wanting to fix exists in the system already. I'm not sure I've ever modified an address at the transaction level.

Once the transaction has been created the address is set, even if you change or update the address record it self it will not update the address in the transaction. One way to do it - 2 prong attacks, update the address record via one update. Then do a transaction update - just reset the original bill to address record selection, this will reload the updated record from the address record and set it in the transaction. I am 100% sure it will work, because one my ex user the buyer used to update the vendor address in the vendor record but it never updated the existing PO for the vendor. So told him to edit the PO and just reselect the address record, it grabs updated data from the vendor ie entity record.